Sang-Keun Gil

2-step Phase-shifting Digital Holographic Optical Encryption and Error Analysis

We propose a new 2-step phase-shifting digital holographic optical encryption technique and analyze tolerance error for this cipher system. 2-step phase-shifting digital holograms are acquired by moving the PZT mirror with phase step of 0 or π/2 in the reference beam path of the Mach-Zehnder type interferometer. Digital hologram with the encrypted information is Fourier transform hologram and is recorded on CCD camera with 256 gray-level quantized intensities. The decryption performance of binary bit data and image data is analyzed by considering error factors. One of the most important errors is quantization error in detecting the digital hologram intensity on CCD. The more the number of quantization error pixels and the variation of gray-level increase, the more the number of error bits increases for decryption. Computer experiments show the results to be carried out encryption and decryption with the proposed method and the graph to analyze the tolerance of the quantization error in the system.

Generation speed and reconstructed image quality enhancement of a long-depth object using double wavefront recording planes and a GPU

A method for fast computer hologram generation for long-depth objects using double wavefront recording planes (WRPs) and a graphics-processing unit (GPU) is presented. The WRPs are placed between the object and the hologram plane. Each WRP records the wavefront from a section of the object. Double WRPs can provide a shorter calculation time and enhanced reconstructed image quality compared with a single WRP, especially for long-depth objects. The average generation speed of two WRPs is 2.5 times that of one WRP. The correlation efficiency of the reconstructed layer relative to the original is 94% for two WRPs and 88.3% for one WRP at the close depth layer.

Development of high-efficiency holographic optical element for LED display

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.

Design of wide angle holographic waveguide monocular head-mounted display using photopolymer

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.

Acquiring multi-viewpoint image of 3D object for integral imaging using synthetic aperture phase-shifting digital holography

We propose a method generating elemental images for the auto-stereoscopic three-dimensional display technique, integral imaging, using phase-shifting digital holography. Phase shifting digital holography is a way recording the digital hologram by changing phase of the reference beam and extracting the complex field of the object beam. Since all 3D information is captured by the phase-shifting digital holography, the elemental images for any specifications of the lens array can be generated from single phase-shifting digital holography. We expanded the viewing angle of the generated elemental image by using the synthetic aperture phase-shifting digital hologram. The principle of the proposed method is verified experimentally.

Demonstration of 10 Gbps Optical Encryption and Decryption by Using Semiconductor Optical Amplifiers

Optical encryption and decryption system is successfully demonstrated by using cross-gain modulation (XGM) technology of semiconductor optical amplifiers (SOAs) all-optical XOR logic gates. Operation speed of 10 Gbps encryption and decryption operations are successfully obtained.

Optical characteristics of an organic-inorganic hybrid photopolymer film for holographic storage and optical application

Monomer diffusion in an organic-inorganic nanocomposite films during the holographic recording was investigated. The photopolymer films with low shrinkage were prepared by dispersing an aromatic methacrylic monomer and a photo-initiator in organic-inorganic hybrid sol-gel matrices. The shrinkage of the photopolymer film and the diffusion of monomers during the holographic recording could be controlled by optimizing the content of an organically modified silica precursor (ORMOSIL) in the sol-gel matrices. The photopolymer film showed high diffraction efficiency (>90%) under an optimized condition. Photo-sensitivity, angular selectivity and application potential for holographic data storage and optical application will be discussed.

Application to optical secret key sharing cryptography using phase-shifting digital holography

We propose a new optical secret key sharing method based on the modified Diffie-Hellman key exchange protocol required in cipher system. The proposed secret key sharing algorithm is optically implemented by 2-step quadrature phase-shifting digital holographic encryption technique using orthogonal polarization. An unknown user’s private key is encrypted into three ciphered digital holograms which are supposed to be opened to the public for secret key sharing. The encrypted digital holograms are Fourier transform holograms and are recorded on CCDs with 256 gray level quantized intensities in the optical setup. The decryption with three ciphered digital holograms reconstructs each user’s private key information, which is used to generate the same shared secret key to each other. The advantage of the proposed method is that the optical setup has a kind of double key encryption scheme and provides the discretion of the user’s private key. The proposed method is very efficient in applying to a secret key sharing cryptosystem with high security strength.

Optical implementation of cipher block chaining mode algorithm using phase-shifting digital holography

Abstract. We propose an optical design of cipher block chaining (CBC) encryption mode using digital holography, which is implemented by the two-step quadrature phase-shifting digital holographic encryption technique using orthogonal polarization. A block of plain text is encrypted with the encryption key by applying the two-step phase-shifting digital holographic method; then, it is changed into cipher text blocks which are digital holograms. Optically, these digital holograms with the encrypted information are Fourier transform holograms and are recorded onto charge-coupled devices with 256 quantization gray levels. This means that the proposed optical CBC encryption is a scheme that has an analog-type of pseudorandom pattern information in the cipher text, while the conventional electronic CBC encryption is a kind of bitwise block message encryption processed by digital bits. Also, the proposed method enables the cryptosystem to have higher security strength and faster processing than the conventional electronic method because of the large two-dimensional (2-D) array key space and parallel processing. The results of computer simulations verify that the proposed optical CBC encryption design is very effective in CBC mode due to fast and secure optical encryption of 2-D data and shows the feasibility for the CBC encryption mode.

Computer-generated holography method based on orthographic projection using depth camera

A orthographic projection image based computer-generated holography method, which is generated from EI(Elemental Image)s pickup by integral photography or CGII(Computer Generation Integral image) is proposed. The proposed method get the continues angular samples of spectrum from depth camera for generate hologram