• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.145-149
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• 2005

We describe holographic ROM system to read bit-type data. It has optical system similar to general optical data storage system such as DVD. But because holographic data storage systems have to adopt imaging optical system, in our system bit-type data can be read out by different servos with DVD. We devised 3-hole method similar to 3- beam method for the tracking servo and used astigmatic optical system for the focusing servo. Also we developed the reference beam servo to measure movement of reference beam because especially holographic data storage systems need reference beam. The system was operated by these three servos and objective lens of NA 0.6. We obtained eye pattern from random data of 3T-2um track pitch. We also obtained another eye pattern from DVD disk by only using focusing servo PDIC in our system to verify the compatibility with DVD.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.418-421
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• 1988

Holographic interferometry is applied in dental research to study the motion of teeth and the deformation of the associated facial structure. We consider double exposure holographic interferometry which has limiting factors such as the stability of fringes, the recording time, the amount of exposure, the localization of fringes and sensitivity. These factors are taken into account to make interferogram. The resulting interferogram gives fringe pattern which is analyzed qualitatively to determine the relative rotation and the deformation of the facial structure.

• Transactions of the Society of Information Storage Systems
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• v.6 no.1
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• pp.25-30
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• 2010

In this paper, we investigate the confocal filter for high quality reading signal of micro holographic data storage system. The confocal filter is used to remove crosstalk effects of adjacent recording-layer by multi-layer multiplexing method. To remove a noise of reading signal, we consider size and geometrical structure of filter. From the obtained results, we present optical characteristics including Fresnel and Fraunhofer diffraction effects. Finally, we propose the optimal confocal filter for good image quality and increased reflection power.

• Transactions of the Society of Information Storage Systems
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• v.6 no.1
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• pp.1-5
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• 2010

Holographic data storage system(HDSS) has many noise sources - crosstalk, scattering and inter pixel interference, etc. Generally the intensity of a light generated from the laser source has Gaussian distribution and this ununiformity of light also can make the data page to have a low SNR. A beam apodizer is used to make the laser as a flat-top beam but the intensity distribution is not strictly uniform. The intensity of light can be controlled using image mask. In this paper the intensity distribution of light used for HDSS is controlled by a digital image mask. The digital image mask is changed arbitrarily in real-time with suggested algorithm for the HDSS.

• Korean Journal of Optics and Photonics
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• v.8 no.1
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• pp.19-25
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• 1997

Holographic zone plate (HZP) is fabricated by interfering a plane wave and a spherical wave in a dichromated gelatin (DCG) film obtained from Agfa 8E75HD plates. We have developed a simple theory for HZP considering optical nonlinearity of DCG material. Analysis of our theory for HZP shows that it has infinite focal points at distances f,f/2, f/3,,…. In experiment, we observed the corresponding focal points of up to f/6 when illuminating HZP by a plane wave. It is also shown that the beam profile around the first focal point measured by using a knife-edge scanning method has a Gaussian shape.

• Bulletin of the Korean Chemical Society
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• v.23 no.4
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• pp.571-574
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• 2002

The photorefractive polymeric composite with good performance was prepared. The carbazole-substituted polysiloxane sensitized by 2,4,7-trinitro-9-fluorenone was used as a photoconducting medium and 1-[4-(2-nitrovinyl)phenyl]piperidine was added as an optically nonlinear chromophore. The photorefractive property of polymer was determined by diffraction efficiency using a 100 ㎛-thick film. The maximum diffraction efficiency ( ηmax) of 71% was obtained at the electric field of 70 V/ ㎛. The potential of the current polymer material as a holographic recording medium was evaluated by the demonstration of holographic recording and subsequent reading of optical image.

• Transactions of the Society of Information Storage Systems
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• v.7 no.2
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• pp.85-89
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• 2011

In retrieving process in angle multiplexing Holographic Data Storage(HDS), It is important to search the exact recording angles. In this paper, we propose the retrieving angle searching method using pre-scan. Pre-scan method is means that rotating the galvano mirror before the retrieving process. Therefore, retrieving signals are maximized when between the galvano mirror and recoded angle are exactly matched. Through the measured signals, we will find the exact angle and compensate tangential tilt angle. The experimental results shows propose method is enough to apply the HDS.

• Journal of information and communication convergence engineering
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• v.11 no.4
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• pp.282-287
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• 2013

A real-time digital holographic display is the core technology for the next-generation 3DTV. Holographic display requires a considerably large amount of calculation. If generating a large number of digital holograms is intended, the amount of calculation and the time required increase exponentially. This is a significant obstacle in a real-time hologram service. This paper proposes an algorithm that increases the speed of generating a Fresnel hologram by using a recursive addition operation covering the entire coordinate array of a digital hologram. The 3D object designed to calculate the digital hologram uses a depth-map image produced by computer graphics. The proposed algorithm is a technique that performs the computer-generated holography (CGH) operation with only recursive addition of all of the hologram's coordinates by analyzing the regularity between the 3D object and the digital hologram coordinates. The experimental results show that the proposed algorithm increases the operation speed by 70% over the technique using the conventional CGH equation and by more than 30% over the previously proposed recursive technique.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.87-90
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• 1999

The dependence of diffraction efficiency as a funct~on of film thickness and incident angle has been investigated in amorphous chalcogenide thin films, which act as a polarization holographic materials. Especially a-(Se, S) based films exhibit a number of photoinduced phenomena not observed in other types of amorphous thin films. Holographic gratings in amorphous As-Ge-Se-S thin films have been formed using the mutual perpendicular polarized(linearly) He-Ne laser light. We could obtain the optimum condition to get high diffraction efficiency.

• Corrosion Science and Technology
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• v.2 no.6
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• pp.277-282
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• 2003

Holographic interferometry, an electromagnetic method, was used to study corrosion of carbon steel, aluminum and copper nickel alloys in NaOH, KCI and $H_2SO_4$ solutions respectively. The technique, called electrochemical emission spectroscopy, consisted of in-situ monitoring of changes in the number of fringe evolutions during the corrosion process. It allowed a detailed picture of anodic dissolution rate changes of alloys. The results were compared to common corrosion measurement methods such as linear polarization resistance measurements and electrochemical impedance spectroscopy. A good agreement between both data was found, thus indicating that holographic interferometry can be a very powerful technique for in-situ corrosion monitoring.