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 a change of the way of object decomposition, reduction of data transfer between the CPU and GPU, kernel integration, stream processing, and utilization of multiple GPUs within a node. The multi-node optimizations include distribution methods of object data from host node to the other nodes. Experimental results show that 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 an execution time of 4.28 sec for generating a 1.6 giga-pixel hologram from a 3.2 giga-pixel object. It means a 237.92 times speed-up of the sequential processing by CPU and 41.78 times speed-up of multi-threaded execution on multicore-CPU, using a conventional FFT-based algorithm.

Computer-generated hologram based on ray-sampling plane method was newly applied to the projection-type holographic display that consists of the holographic projection and the holographic optical element screen. In the proposed method, geometric deformation characteristic of the holographic image via the display system was mathematically derived and canceled out by the coordinate transformation of ray-sampling condition to avoid the image distortion. In the experiment, holographic image reconstruction with the arbitral depth expression without image distortion could be optically demonstrated.

Direct-binary search method has been used for converting complex holograms into binary format. However, this algorithm is optimized to reconstruct monochromatic digital holograms and is accurate only in a narrow-depth range. In this paper, we proposed an advanced direct-binary search method to increase the depth of field of 3D scenes reconstructed in RGB by binary holograms.

Head-mounted displays (HMDs) and augmented reality (AR) are actively being studied. However, ordinary AR HMDs for visual assistance have a problem in which users have difficulty simultaneously focusing their eyes on both the real target object and the displayed image because the image can only be displayed at a fixed distance from an user's eyes in contrast to where the real object three-dimensionally exists. Therefore, we considered incorporating a holographic technology, an ideal three-dimensional (3D) display technology, into an AR HMD system. A few studies on holographic HMDs have had technical problems, and they have faults in size and weight. This paper proposes a compact holographic AR HMD system with the purpose of enabling an ideal 3D AR HMD system which can correctly reconstruct the image at any depth. In this paper, a Fourier transform optical system (FTOS) was implemented using only one lens in order to achieve a compact and lightweight structure, and a compact holographic AR HMD system was constructed. The experimental results showed that the proposed system can reconstruct sharp images at the correct depth for a wide depth range. This study enabled an ideal 3D AR HMD system that enables simultaneous viewing of both the real target object and the reconstructed image without feeling visual fatigue.

This study involves proposing a high-speed computer-generated hologram playback by using a digital micromirror device for high-definition spatiotemporal division multiplexing electroholography. Consequently, the results indicated that the study successfully reconstructed a high-definition 3-D movie of 3-D objects that was comprised of approximately 900,000 points at 60 fps when each frame was divided into twelve parts.

This paper presents an application of low-coherence interferometry for measurement of mode field diameters (MFDs) of a few-mode fiber and shows its performance compared with another method using a mode multiplexer. We found that the presented method could measure MFDs in a few-mode fiber even without any special mode multiplexers.

In this paper, we propose a passive imaging system for noise-source identification using time-domain waveform sampling. The fundamental concepts are based on optics theory. A waveform of a diffracted field over an entrance pupil is obtained by a digitizing oscilloscope. The phase distributions over the entrance pupil for each frequency are calculated by using Fourier transform of the acquired waveforms. Thus, an image on the focal plane is reconstructed by using inverse Fresnel transform. The most significant advantage of the proposed method is that an image for each frequency can be obtained separately. We confirmed that the proposed method can be used for practical noise-source identification, by experimentally obtaining images for an emission from personal computers.

Angle-multiplexed holography using four-wave mixing (4WM) was demonstrated with a monolithic photorefractive carbazole trimer. We measured the diffraction efficiency as a function of incident angle of the read beam. The cross-talk was almost negligible at the Bragg angle mismatch of 1. Two figure images were recorded with the different incident angle of the reference beam in the photorefractive carbazole trimer film, and were read out independently by illuminating with the read beam which counter-propagated to the corresponding reference beam.

A Fourier-optics based imaging system for electromagnetic interference (EMI) sources is presented. It is necessary to decrease undesired emissions in order to meet EMI requirements. To investigate this problem, a visualization of electromagnetic (EM) emitting fields is very useful. In this paper, we propose a passive imaging system of EM emitting fields based on Fourier optics. Amplitude and phase values of diffracted fields on an entrance pupil are acquired by using a six-port interferometer. The measured EM fields are then processed on a computer, and an image is retrieved using an inverse Fresnel transform. Experiments are presented, which demonstrate the potential of the proposed method. The proposed system is useful not only in the field of electromagnetic compatibility (EMC), but also for scientific elucidation to discuss the optics and microwave theory of the same viewpoint.

The visual reality of a holographic image has improved effectively by utilizing multicolor reconstruction procedure. This fact is applicable to a real-time three-dimensional display for a computer generated hologram (CGH). However, it is quite difficult to generate a CGH for multicolor imaging in real-time because a CGH contains essentially a huge amount of information, and increases further information produced by multiplying the number of primary colors for multicolor imaging. Moreover, the optical system is considerably complicated for the multicolor image reconstruction. In this paper, a new method is presented to reconstruct a three dimensional multicolor image from a CGH. In this method, three sub-holograms to reconstruct the primary color images are sampled respectively for reducing the amount of computation and realizing a simple optical system. Fringe patterns are displayed by only one spatial light modulator (SLM) and color crosstalk images are eliminated by a color filtering system for ensuring that each sub-hologram can be only illuminated by the light with an appropriate color. A multicolor imaging method from a CGH is proposed and also the experimental results are shown.

A novel method for image reconstruction of a microwave hologram synthesized from one-dimensional data is proposed. In the data acquisition, an emitting antenna is shifted along a line. At every position of the emitting antenna, the amplitude and phase of diffraction fields are measured with a detecting antenna along a line perpendicular to the shifted direction. An equivalent two-dimensional diffraction field is synthesized from the one-dimensional data sets. The conventional reconstruction method applied to the one-dimensional configuration was the Fresnel approximation method. In this paper, an equivalent diffraction is introduced in order to obtain better images than the Fresnel approximation. An experiment made at 10 GHz shows the usefulness of the proposed method.

Several methods have be proposed or used to optimize the phase distribution of a kinoform. In this paper, we proposed a fast algorithm for optimization of the kinoform based on simulated annealing to reduce the large computation cost. This method uses a simplified equation to calculate the energy function after perturbation.

A real-time read/write motion picture has been demonstrated by hole-burning holography using cryogenic Eu3+: Y2SiO5 crystal. In a holographic configuration the laser frequency was continuously scanned within the 7F0-5D0 absorption line while the object was in motion. This movie has no picture frames, and therefore is temporally continuous. This feature allows realization of high-speed and high-time-resolution motion recording.

Theoretical and experimental results are presented for angle-multiplexed and wavelength-multiplexed holographic recording. The recording medium is a cerium doped Sr1-XBaXNb2O6 (SBN) single crystal, and the light sources are a laser diode excited second harmonic generation (SHG) laser and a tunable laser diode. The SBN single crystal has high recording sensitivity, high diffraction efficiency and high temperature stability. The laser diodes miniaturize the holographic recording system. Crosstalk between hologram pages is theoretically calculated by using modified coupled-wave equations, and is also experimentally measured. The experimental results agree well with the theoretical results. Two-dimensional alphabetical character images are recorded using angle- and wavelength-multiplexed holographic methods, and are successfully reconstructed. The theoretical results indicate that several hundred multiplexed holograms can be recorded with little crosstalk using the proposed system. This multiplexed holographic recording technique will enable high-density recording and high data-transfer rates.

A best-fit panel model in the radio holographic metrology taking into account locations and sizes of actual surface panels in a large reflector antenna is presented. A displacement and tilt of each panel can be estimated by introducing the best-fit panel model. It was confirmed by simulations that the distinction can be drawn between a continuous surface error and a discontinuous one. Errors due to truncation of the radiation pattern were calculated by simulations. It was found that a measurement of a 128128 map is optimum for the 45-m telescope. The reliability of the measurements using this model was examined by experiments with panel displacements. Panel adjustments using the best-fit panel model successfully improved the surface accuracy of the antenna from 138µm rms to 84µm rms (/D=210-6).

The authors developed new measuring system (Holographic Pattern Measuring System [HPMS]), which is composed of both techniques of holography and graphic image processing, was used to measure the vibrations of a printed circuit board (PCB) due to operation of a mounted electromagnetic relay on it. The clear vibration patterns were obtained. By using pattern analysis processor, quantitative vibration patterns of the PCB surface were observed. Both the vibration patterns and displacements were changed by edge fixing way of the PCB.