In this paper, we propose a robust 3D image encryption scheme based on computer-generated hologram (CGH) in fractional Fourier domain. The layer-based Fresnel transform is utilized to generate one phase-only CGH, which is then decomposed into two phase-only masks (POMs) by pixel superimposed method. Encryption was realized by using the created POMs in two cascaded fractional Fourier transform domains while two decryption keys are produced in the encryption process. The cryptosystem is asymmetric and high resistance against to the various potential attacks, including chosen-plaintext attack (CPA). The proposal is supported with computer simulation results. Simulation results and security analysis verify the feasibility and effectiveness of the proposed encryption scheme.
We proposed a novel scheme to achieve a computer-generated hologram (CGH). The CGH is generated from a point cloud that is transformed by a mapping relationship of a series of sub-images. The sub-images are converted from elemental images captured by integral imaging pickup system. A more continues depth map can be obtained and a clearer display of the 3D scene can be presented. Moreover, the inherent drawback pseudoscopic problem of integral imaging can also be overcome.
In this paper, the design and produce of the wedge-shaped waveguide head-mounted display (HMD) based on reflection holographic optical element (RHOE) are described. A variety of factors were considered when designing, such as loss of efficiency, volume, wide field of view (FOV), and eye box. The thickness of the designed wedge-shaped waveguide can be reduced to two times in comparison with the system that uses the conventional reflective optics in the waveguide. The measured optical efficiency of the monocular HMD using HOE is 34%, with 15° FOV and a large eye box. The results confirm that the designed and fabricated waveguide can be employed in future commercial HMD.
Holographic optical element (HOE) have classically been designed using grating theory, logically so, since an HOE is a grating produced on film by two interfering beams of coherent light. This paper describes the development of full color HOE recorded on aspherical substrate using a photopolymer. The reflection HOE was evaluated by measuring the diffraction efficiencies of holographic volume gratings recorded individually at 633 nm, 532 nm, and 473nm wavelengths. The spectral characterization of the HOE, recorded using a combined single beam, and recorded using sequential beam, was carried out. Practical methods for fabrication of high efficiency aspheric HOE by single layer photopolymer were developed.
In this paper, we present the development of full color holographic optical element for light-emitting diodes display application using a photopolymer. The reflection HOE was evaluated by measuring the diffraction efficiencies of holographic volume gratings recorded individually at 633 nm, 532 nm, and 473nm wavelengths. The spectral characterization of the holographic optical element, recorded using a combined single beam, and recorded using sequential beam, was carried out. Practical methods for fabrication of high efficiency holographic optical element by single layer photopolymer were developed. As the reconstruction light source of the hologram, light-emitting diodes of 632nm, 523nm and 465nm in wavelength was used. The results represent a strong confirmation that the special recording method using photopolymer can be employed in future commercial holographic applications.
Viewing angle of the conventional flat hologram is not very large (less than 180°) attributed to their planar observation surface. If we want to synthesize a wide view computer generated hologram, a numerical simulation of the diffraction on the non-planar observation surfaces is required, computer generated cylindrical hologram (CGCH) can be a solution. Approximately 2,500 object points were used for this research. We have realized a CGCH that is viewable in 360°. However, the heavy computation load is one of the issues. Therefore, we propose a fast calculation method for a computer generated cylindrical hologram by the use of wave-front recording surface. The wave-front recording surface is placed between the object data and a CGCH. When the wave-front recording surface is placed close to the object, the object light passes through a small region on the wave recording surface. Therefore the computational complexity for the object light is very small. We can obtain a CGCH to execute diffraction calculation from the wave-front recording surface, propagating the recorded optical field of the wave-front recording surface to the cylindrical hologram surface using only two FFT operations and hence is much faster.
In this paper an application of the Holographic Optical Element (HOE) which is designed by using the photopolymer is
proposed. Using the HOE to replace two optic elements of the conventional HMD is possible to reduce the volume and
weight. In order to implement the proposed system, we analyze the optical characteristics of the photopolymer and
confirm the optimum recording condition of the HOE. The proposed system is verified experimentally.
In this paper, we present an analysis on space bandwidth product of digital hologram. The condition for clear
reconstruction of in-axis and off-axis digital hologram case is derived. The correlation efficiency and modulate transfer
function (MTF) are then used for quantitative analysis of the reconstruction object. The presented analysis is verified by
simulation result and then is applied to record and reconstruct video hologram.
In this study we have exploited the parallel nature of the computations involved in the process of numerical volume
reconstruction of three-dimensional digital holographic microscopy and utilized CUDA enabled graphics processing
unit (GPU) to accelerate the reconstruction process. We have recorded holograms of the 3D specimen using CCD
with inline setup, then using GPU we have initiated CUDA kernels for de-convolution of the diffraction integral for
multiple depth planes in parallel, speeding up the reconstruction of the entire volume. Our experimental results
confirm that GPU reconstruction is much faster than that of central processing unit (CPU).
In this paper, we demonstrate the application of the spiral phase filter for image enhancement in phase shifting digital
holographic microscopy system. The method is based on Fourier plane filtering of the microscopic image with a spiral
phase filter which is located at a computer controlled Spatial Light Modulator (SLM) in the optical imaging pathway of
phase shift digital holographic microscopy system. Spiral phase filter is designed by radial isotropic Hilbert transform.
The spiral phase filter as a spatial filter in Fourier plane of an imaging setup has been proposed as an isotropic edge
detection method providing strong contrast enhancement of microscopic amplitude and phase objects. Since all threedimensional
information is captured by phase shifting digital holographic microscopy, the reconstructed phase object or
cell is reconstructed clearly observed in three-dimension.
A technique displaying arbitrary images based on phase contrast imaging with phase optimization method is proposed.
Phase optimization is performed in a way similar to the iterative Fourier transform algorithm which considers the phase
shift and the aperture size of the phase contrast filter. We test and compare two phase shift cases, which are π/2 and π, in
optimization process. The phase contrast filter at the Fourier plane is implemented using photopolymer whose optically
induced refractive index change has a linear dependence on the illuminating light intensity. As a result, the proposed
method is capable of displaying arbitrary images with enhanced quality and high light efficiency in phase contrast
projection field. Also when the phase contrast filter has π phase shift, the enhancement of the output intensity image is
more obvious.
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