• Journal of the Optical Society of Korea
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• v.18 no.2
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• pp.146-150
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• 2014

We propose an experimental holographic imaging scheme combining compressive sensing (CS) theory with digital holography in phase-shifting conditions. We use the Mach-Zehnder interferometer for hologram formation, and apply the compressive sensing (CS) approach to the holography acquisition process. Through projecting the hologram pattern into a digital micro-mirror device (DMD), finally we will acquire the compressive sensing measurements using a photodiode. After receiving the data of two holograms via conventional communication channel, we reconstruct the original object using certain signal recovery algorithms of CS theory and hologram reconstruction techniques, which demonstrated the feasibility of the proposed method.

• Korean Journal of Optics and Photonics
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• v.19 no.5
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• pp.360-364
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• 2008

The diffraction efficiencies of gratings are affected by the inner structure which is determined by modulation type. CGH (Computer generated Hologram) basically uses the principles of a diffraction grating. As like as the diffraction gratings the patterns recorded in the CGH are different according to modulation methods which result in the performances of the reconstructed images. In this paper, on this fact CGHs are recorded according to sinusoidal and rectangular modulation methods and the characteristics of reconstructed images are analyzed. Also the reconstruction performances of the amplitude and phase, phase-only and binary phase CGH are analyzed.

• Current Optics and Photonics
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• v.4 no.2
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• pp.115-120
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• 2020

A novel method is proposed for controlling the distance of an image plane in Fourier holograms using varifocal electric-field-driven liquid-crystal (ELC) lenses. Phase Fresnel lenses are employed to reduce the thickness and response time of the ELC lenses. The voltages applied to the electrodes of the ELC Fresnel lens are adjusted so that the lens has the same retardation distribution as an ideal lens. The focal length can be controlled by changing the retardation distribution with the applied voltages. Simulations were conducted for the image reconstruction of Fourier holograms with various focal lengths of the ELC Fresnel lenses. The simulation results indicate that the distance of the image plane can be properly controlled with the varifocal ELC Fresnel lens.

• Journal of KSNVE
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• v.9 no.1
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• pp.131-140
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• 1999

A method to reconstruct the sound field around a Korean bell is developed. The sound radiation problem is formulated based on the boundary element method by using the algorithm of the acoustical holography. Sound pressures at the hologram surface are measured and used as input data for the analysis program that was developed in this study. An error minimization scheme is presented to overcome difficulties that arise in the backward reconstruction of the BEM-based acoustical holography In the model fictitious source surfaces were also introduced to reduce the complexity stemmed from the source shape. The sound field associated with the (4.0) vibrational mode of the Korean bell was visualized and verified experimentally.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.1-7
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• 2002

We derived the resolution of the modified triangular interferometer and described the analysis about distance measurement using the one. Also, to demonstrate the feasibility of distance measurement using the modified triangular interferometer, the incoherent hologram of a two-point source with depth and its numerical reconstruction were presented. We demonstrated the possibility of the modified triangular interferometer as a three-dimensional display by recording and reconstructing the incoherent hologram of three-dimensional image.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.958-961
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• 1999

A new image encoding and identification scheme is proposed for security verification by using CGH(computer generated hologram), random phase mask, and correlation technique. The encrypted image, which is attached to the security product, is made by multiplying QPH(quadratic phase hologram) using SA(simulated annealing) algorithm with a random phase function. The random phase function plays a role of key when the encrypted image is decrypted. The encrypted image could be optically recovered by 2-f system and automatically verified for personal identification. Simulation results show the proposed method cand be used for the reconstruction and the recognition of the encrypted. Image.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.818-819
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• 2013

This paper propose a contents security technique for digital holographic display service. Digital holographic video system assumes the existing service frame for 2-dimensional or 3-dimensional video, which includes data acquisition, processing, transmission, reception, and reconstruction. In this paper, we perform the encryption of RGB image and depth-map for such a system. The experimental results showed that encrypting only 0.048% of the entire data was enough to hide the constants of the RGB image and depth-map.

• Journal of the Optical Society of Korea
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• v.4 no.1
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• pp.19-22
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• 2000

A new image encoding and identification scheme is proposed for security verification by us-ing a CGH(computer generated hologram), random phase mask, and a correlation technique. The encrypted image, which is attached to the security product, is made by multiplying a QP- CGH(quadratic phase CGI) with a random phase function. The random phase function plays a key role when the encrypted image is decrypted. The encrypted image can be optically recovered by a 2-f imaging system and automatically verified for personal identification by a 4-f correlation system. Simulation results show the proposed method can be used for both the reconstruction of an original image and the recognition of an encrypted image.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.274-281
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• 1995

The new method of recording and reconstructing a synthetic object, which was called as scannedobject holography (SOH), was proposed and its feasibility was demonstrated theoretically and experimentally. The hologram was recorded by interfering the fixed reference beam with spherical waves emitting from a moving point source, whose trajectory determined the shape of the synthetic object to be recorded. The end face of an optical fiber and the output from a pulsed laser were utilized in order to implement a moving point source experimentally. tally.

• Current Optics and Photonics
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• v.2 no.6
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• pp.547-553
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• 2018

In this paper, a new method for spatial filtering in digital holography is proposed and verified by simulations compared to conventional methods. The new method is based on the simultaneous acquisition of two digital holograms, which can be separated by distinct spatial modulation, in a single image. Two holograms are generated by two reference waves, which have different spatial modulation orientations. Then, the overlapping region between the DC term and the object wave in the first hologram can be replaced with a less-overlapping region of the object wave in the second hologram because the whole image contains two holograms where the same objective wave has been recorded. In the simulation results, it is confirmed that the reconstructed image by the new method has better quality than for the original method.