• Journal of the Optical Society of Korea
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• v.9 no.1
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• pp.26-31
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• 2005

We describe the design and the implementation of video-rate reflection confocal scanning microscopy (CSM) using an acousto-optical deflector (AOD) for the fast horizontal scan and a galvanometer mirror (GM) for the slow vertical scan. Design parameters of the optical system are determined for optimal resolution and contrast. The OSLO simulations show that the performances of CSM are not changed with deflection angle and the wavefront errors of the system are less than 0.012λ. To evaluate the performances of designed CSM, we do a series of tests, measuring lateral and axial resolution, real time image acquisition. Due to a higher axial resolution compared with conventional microscopy, CSM can detect the surface of sub-micrometer features. We detect 138㎚ line shape pattern with a video-rate (30 frm/sec). And 10㎚ axial resolution is archived. The lateral resolution of the topographic images will be further enhanced by differential confocal microscopy (DCM) method and computational algorithms.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3115-3123
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• 1993

This paper presents a real-time correction method of the movemont errors of a translatory precision machine axis. This method is a null-balances technique in which two plane mirrors are used to generate an interferometric fringe pattern utilizing the optical principles of TwymanGreen interferometry. One mirror is fixed on a reference frame, while the other is placed on the machine axis being supported by three piezoelectric actuators. From the fringe pattern, one translatory and two rotational error components of the machine axis are simultaneously detected by using CCD camera vision and image processing techniques. These errors are then independently suppressed by activating the peizoelectric actuators by real-time feedback control while the machine axis is moving. Experimental results demonstrate that a machine axis can be controlled with movement errors less than 10 nm in vertical straightness, 0.1 arcsec in pitch, and 0.06 arcsec in roll for 50mm travel by adopting the real-time correction method.

• Journal of Astronomy and Space Sciences
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• v.29 no.2
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• pp.199-208
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• 2012

The world's first geostationary ocean color imager (GOCI) is a three-mirror anastigmat optical system 140 mm in diameter. Designed for 500 m ground sampling distance, this paper deals with on-orbit modulation transfer function (MTF)measurement and analysis for GOCI. First, the knife-edge and point source methods were applied to the 8th band (865 nm) image measured April 5th, 2011. The target details used are the coastlines of the Korean peninsula and of Japan, and an island 400 meters in diameter. The resulting MTFs are 0.35 and 0.34 for the Korean East Coastline and Japanese West Coastline edge targets, respectively, and 0.38 for the island target. The daily and seasonal MTF variations at the Nyquist frequency were also checked, and the result is $0.32{\pm}0.04$ on average. From these results, we confirm that the GOCI on-orbit MTF performance satisfies the design requirements of 0.32 for 865 nm wavelength.

• Publications of The Korean Astronomical Society
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• v.11 no.1
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• pp.163-175
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• 1996

We propose the development and test result of new optical axis alignment system for the interchangeable F/8 secondary mirror of the BOAO 1.8m telescope system. Since the original system was not equipped with a suitable optical alignment facility, the whole alignment process was performed by hand. It was necessary at least three persons working more than 2 nights and the altitude of the telescope could not exceed 10 degrees, in such altitude the alignment quality was not so good by atmospheric effect. The new system adopts position readable motorized system and remote control operation by the computer installed in observation room, which reduces the number of workers to only one and eliminates the altitude restriction. The defocused CCD image pair obtained at higher altitude makes the aberration estimates more accurately and the number of required alignment loops is reduced from 10 to 4. The system has been installed on September 1, and performed alignment three times. The test results show that the system is stable and accurate, gives better optical performance of the telescope under F/8 focus. We hope to emphasize the fact that the new system will increase observation time of the telescope by about 20 nights per year assuming one alignment in every month.

• Journal of the Korea Society of Computer and Information
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• v.4 no.3
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• pp.60-66
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• 1999

The purpose of this study is to design and materialize the simulated courseware which is based on new educational environments and student-based education. The scope of this study is reflection and refraction of in the physics of high school. This paper introduce the theoretical background of courseware and investigate the structure and process of the teaching-theory by visualized computer simulation. We applied the basic concept about the reflection and refraction of light and explained the simulated images of spherical mirror and lens with the principles expressions and relative image forms. The last we simulated the various kinds of the images, shapes and distance of the images by changing the distance of object and focus which are made by computer simulation.

• Journal of Electrical Engineering and Technology
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• v.2 no.2
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• pp.274-279
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• 2007

This study focuses on the enhancement of maskless photolithography as well as the peptide synthesis application with single crystalline silicon micromirrors. A single crystalline silicon micromirror array has been designed and fabricated in order to improve its application to the peptide synthesis. A micromirror rotates about ${\pm}\;9^{\circ}$ at the pull-in voltage, which can range from 90.7 V to 115.1 V. A $210\;{\mu}m-by-210\;{\mu}m$ micromirror device with $270\;{\mu}m$ mirror pitch meets the requirements of an adequately precise separation for peptide synthesis. Synthetic 16 by 16 peptide array corresponds to the same number of micromirrors. The large size of peptide pattern and the separation facilitate biochip experiments using fluorescence assay. The peptide pattern has been synthesized on the GPTS-PEG200 surface with BSA-blocking and thereupon the background was acetylated to reject non-specific bindings. Hence, an averaged slope at the pattern edge has been distinguishably improved in comparison to patterning results from an aluminum micromirror.

• ETRI Journal
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• v.44 no.1
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• pp.51-61
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• 2022

In this paper, we introduced a novel voxel-wise UV parameterization and view-dependent texture synthesis for the immersive rendering of a truncated signed distance field (TSDF) scene model. The proposed UV parameterization delegates a precomputed UV map to each voxel using the UV map lookup table and consequently, enabling efficient and high-quality texture mapping without a complex process. By leveraging the convenient UV parameterization, our view-dependent texture synthesis method extracts a set of local texture maps for each voxel from the multiview color images and separates them into a single view-independent diffuse map and a set of weight coefficients for an orthogonal specular map basis. Furthermore, the view-dependent specular maps for an arbitrary view are estimated by combining the specular weights of each source view using the location of the arbitrary and source viewpoints to generate the view-dependent textures for arbitrary views. The experimental results demonstrate that the proposed method effectively synthesizes texture for an arbitrary view, thereby enabling the visualization of view-dependent effects, such as specularity and mirror reflection.

• Journal of Astronomy and Space Sciences
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• v.40 no.4
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• pp.237-245
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• 2023

Laser communication has been considered as a novel method for earth observation satellites with generation of high data volume. It offers faster data transmission speeds compared to conventional radio frequency (RF) communication due to the short wavelength and narrow beam divergence. However, laser beams are refracted due to atmospheric turbulence between the ground and the satellite. Refracted laser beams, upon reaching the receiver, result in angle-of-arrival (AoA) fluctuation, inducing image dancing and wavefront distortion. These phenomena hinder signal acquisition and lead to signal loss in the course of laser communication. So, precise alignment between the transmitter and receiver is essential to guarantee effective and reliable laser communication, which is achieved by pointing, acquisition, and tracking (PAT) system. In this study, we simulate the effectiveness of tip/tilt compensation for more efficient laser communication in the satellite-ground downlink. By compensating for low-order terms using tip/tilt mirror, we verify the alleviation of AoA fluctuations under both weak and strong atmospheric turbulence conditions. And the performance of tip/tilt correction is analyzed in terms of the AoA fluctuation and collected power on the detector.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.67-67
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• 2003

It is crucial to minimize setup errors of a cancer treatment machine using a high energy and to perform precise radiation therapy. Usually, port film has been used for verifying errors. The Korea Cancer Center Hospital (KCCH) has manufactured digital electronic portal imaging device (EPID) system to verify treatment machine errors as a Quality Assurance (Q.A) tool. This EPID was consisted of a metal/fluorescent screen, 45$^{\circ}$ mirror, a camera and an image grabber and could display the portal image with near real time KIRAMS has also made the acrylic phantom that has lead line of 1mm width for ligh/radiation field congruence verification and reference points phantom for using as an isocenter on portal image. We acquired portal images of 10$\times$10cm field size with this phantom by EPID and portal film rotating treatment head by 0.3$^{\circ}$, 0.6$^{\circ}$ and 0.9$^{\circ}$. To check field size, we acquired portal images with 18$\times$18cm, 19$\times$19cm and 20$\times$20cm field size with collimator angle 0$^{\circ}$ and 0.5$^{\circ}$ individually. We have performed Flatness comparison by displaying the line intensity from EPID and film images. The 0.6$^{\circ}$ shift of collimator angle was easily observed by edge detection of irradiated field size on EPID image. To the extent of one pixel (0.76mm) difference could be detected. We also have measured field size by finding optimal threshold value, finding isocenter, finding field edge and gauging distance between isocenter and edge. This EPID system could be used as a Q.A tool for checking field size, light/radiation congruence and flatness with a developed video based EPID.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.429-440
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• 2004

Recently, real time data acquisition become important for space weather forecast and research. In this work, we have developed the data acquisition tools and their applications for space weather monitoring. We have developed programs to download the space weather data using IDL as well as programs to interactively display the image and data using ION (IDL on the Net). By using these tools, we have constructed the mirror site of Active Region Monitor (ARM) which summarizes several different solar activities, and developed ION programs to display TEC(Total Electron Contents) maps from GPS data at the passage of Korean satellites. At present, the KAO ARM mirror site (http://sun.kao.re.kr/arm) is successfully updated in every thirty minutes. The TEC maps from GPS data are expected to be used for monitoring the space environment of Korean satellites.