• Journal of the Optical Society of Korea
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• v.19 no.1
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• pp.29-37
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• 2015

The wavefront printer records a volume-reflection hologram as a two-dimensional array of elemental holograms from computer-generated holograms (CGHs) displayed on a spatial light modulator (SLM). The wavefront coming from the object is extracted by filtering in the spatial-frequency domain. This paper presents a method to improve color reproduction in a wavefront printer with spatial division of exposures at primary colors, by adaptive partitioning of the SLM in accordance with the color content encoded in the input CGHs, and by the controllable change of exposure times for the recording of primary colors. The method is verified with a color wavefront printer with demagnification of the object beam. The quality of reconstruction achieved by the proposed method proves its efficiency in eliminating the stripe artifacts that are superimposed on reconstructed images in conventional mosaic recording.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.4
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• pp.37-45
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• 2001

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.286-287
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• 2003

Polarization-sensitive optical coherence tomography (PS-OCT) was developed to image highly scattering tissues with accounting for polarization effects in the sample. These polarization-sensitive images can provide additional information on the structure of the tissue because of a polarization state of the light is changed at its interaction with biological tissues. The scattering and birefringence are two phenomena, which change the polarization state of light passing through medium. (omitted)

• Conservation Science in Museum
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• v.28
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• pp.51-64
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• 2022

This study aims to identify the impact of optical energy on cultural properties when the light energy irradiates cultural assets during augmented reality (AR) or media façade performances as activities designed to garner public interest. The 10-story Gyeongcheonsa Pagoda was used for this study, and the impact was evaluated by comparing the optical energy irradiated during a media façade performance with the energy irradiated under normal conditions. For comparison, this study measured the illuminance in lux for each light source that irradiated the ten-story stone pagoda and used the data to calculate illuminance in lux-hours. The results showed that the pagoda receives 786.4 lux per hour when both sunlight and artificial light are present, while 13.2 lux of energy is irradicated by the media façade for each performance. The result indicates that the pagoda receives about 29.8 times more optical energy from sunlight and artificial light sources than during media façade performances on an hourly basis, when the performance is carried out twice a week. This study therefore concludes that the optical energy of media façade performances inflicted trivial damage to the ten-story stone pagoda.

• Journal of the Korean Graphic Arts Communication Society
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• v.29 no.3
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• pp.97-104
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• 2011

The storing ability of information of optical disks directly depends on the physical property of recording unit cells. It means that the degradation of optical disks ultimately causes the loss of the physical and chemical properties of recording unit cells and leads also information, too. We investigated the degradation and life time of optical disks which tell us the longevity of the preservation of information. Optical disks were aged using the accelerated aging system and studied by optical reflectivity spectroscopy and atomic force microscopy(AFM), and the preservation environment of electronic media in National central library of Korea also were analysed. Results show that the double reflective coated optical disks have good preservation of recording information but revealed some deformation of dye area in the AFM images. It means that we should include the mechanical and chemical degradation of the optical disks in the life time expectation evaluation.

• Journal of Korea Multimedia Society
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• v.21 no.8
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• pp.829-836
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• 2018

This study attempts to detect a shot boundary in films(or dramas) based on the length of a sequence. As films or dramas use scene change effects a lot, the issues regarding the effects are more diverse than those used in surveillance cameras, sports videos, medical care and security. Visual techniques used in films are focused on the human sense of aesthetic therefore, it is difficult to solve the errors in shot boundary detection with the method employed in surveillance cameras. In order to define the errors arisen from the scene change effects between the images and resolve those issues, the mixed algorithm based upon color histogram, edge histogram, and optical flow was implemented. The shot boundary data from this study will be used when analysing the configuration of meaningful shots in sequences in the future.

• Smart Media Journal
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• v.5 no.1
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• pp.78-87
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• 2016

The major problems of recent object tracking methods are related to the inefficient detection of moving objects due to occlusions, noisy background and inconsistent body motion. This paper presents a robust method for the detection and tracking of a moving in infrared animal videos. The tracking system is based on adaptive optical flow generation, Gaussian mixture and Kalman filtering. The adaptive Gaussian model of optical flow (GMOF) is used to extract foreground and noises are removed based on the object motion. Kalman filter enables the prediction of the object position in the presence of partial occlusions, and changes the size of the animal detected automatically along the image sequence. The presented method is evaluated in various environments of unstable background because of winds, and illuminations changes. The results show that our approach is more robust to background noises and performs better than previous methods.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.59-63
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• 2005

Nowadays, various approaches are performed to increase the storage capacity of optical storage device. One of the promising candidates is using the high NA lens. By using high NA lens, the beam spot size can be reduced which will lead to increase the storage density. This paper proposes a double cantilever beam type bimorph PZT actuator for fine motion that can control the gap between the flexible media and optical pickup which uses high NA lens. Mathematical model is derived by using Hamilton's principle and the model is verified by finite element analysis and experiment. Position controller is designed and its performance is evaluated by experiment.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.1
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• pp.47-53
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• 1999

CD-ROM(Compact Disk-Read Only Memory) is very attractive storage media because it has much storage space but is small size and portable. Optical pickup, one of the most important parts for reading data on a CD-ROM, is not produced tuned up. For the use of goods, we must tune up the optical pickup by adjusting the screw for adjustment. First, we developed analog servo system for optical pickup tuners. For eliminating some problems in analog servo system, this paper designed the modeling of digital servo system for optical pickup tuner. Though the characteristics of optical pickup are changed, the digital servo system for optical pickup tuner can easily apply to all pickup, and can reduce the measurement error among the optical pickup tuners. For the purpose of confirming the designed digital servo system, we produced data that specify the disk vibration and the disk eccentricity, and simulated servo system with MATLAB.

• ETRI Journal
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• v.38 no.4
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• pp.665-674
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• 2016

We designed and fabricated a semiconductor optical amplifier-integrated dual-mode laser (SOA-DML) as a compact and widely tunable continuous-wave terahertz (CW THz) beat source, and a pin-photodiode (pin-PD) integrated with a log-periodic planar antenna as a CW THz emitter. The SOA-DML chip consists of two distributed feedback lasers, a phase section for a tunable beat source, an amplifier, and a tapered spot-size converter for high output power and fiber-coupling efficiency. The SOA-DML module exhibits an output power of more than 15 dBm and clear four-wave mixing throughout the entire tuning range. Using integrated micro-heaters, we were able to tune the optical beat frequency from 380 GHz to 1,120 GHz. In addition, the effect of benzocyclobutene polymer in the antenna design of a pin-PD was considered. Furthermore, a dual active photodiode (PD) for high output power was designed, resulting in a 1.7-fold increase in efficiency compared with a single active PD at 220 GHz. Finally, herein we successfully show the feasibility of the CW THz system by demonstrating THz frequency-domain spectroscopy of an ${\alpha}$-lactose pellet using the modularized SOA-DML and a PD emitter.