• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.49.1-49.1
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• 2014

The NISS (Near-infrared Imaging Spectrometer for Star formation history) onboard NEXTSat-1 is the near-infrared instrument onboard NEXTSat-1 which is being developed by KASI. The imaging low-resolution spectroscopic observation in the near-infrared range for nearby galaxies, low background regions, star-forming regions and so on will be performed on orbit. After the System Requirement Review, the optical design is changed from on-axis to the off-axis telescope which has a wide field of view (2 deg. ${\times}$ 2 deg.) as well as the wide wavelength range from 0.95 to $3.8{\mu}m$. The mechanical structure is considered to endure the launching condition as well as the space environment. The design of relay optics is optimized to maintain the uniform optical performance in the required wavelength range. The stray light analysis is being made to evade a light outside a field of view. The dewar is designed to operate the infrared detector at 80K stage. From the thermal analysis, we confirmed that the telescope can be cooled down to around 200K in order to reduce the large amount of thermal noise. Here, we report the current status of the NISS development.

• Journal of the Optical Society of Korea
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• v.14 no.3
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• pp.215-220
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• 2010

Aerosol observation with Raman LIDAR in NIES (National Institute for Environmental Studies, Japan) LIDAR network was conducted from 17 April to 12 June 2008 over Beijing, China. The aerosol optical properties derived from Raman LIDAR were compared with the retrieved data from sun photometer and sky radiometer observations in the Aerosol Robotic Network (AERONET). The comparison provided the complete knowledge of aerosol optical and physical properties in Beijing, especially in pollution and Asian dust events. The averaged aerosol optical depth (AOD) at 675 nm was 0.81 and the Angstrom exponent between 440 nm and 675 nm was 0.99 during experiment. The LIDAR derived AOD at 532 nm in the planetary boundary layer (PBL) was 0.48, which implied that half of the total AOD was contributed by the aerosol in PBL. The corresponding averaged LIDAR ratio and total depolarization ratio (TDR) were 48.5sr and 8.1%. The negative correlation between LIDAR ratio and TDR indicated the LIDAR ratio decreased with aerosol size because of the high TDR associated with nonspherical and large aerosols. The typical volume size distribution of the aerosol clearly demonstrated that the coarse mode radius located near 3 ${\mu}m$ in dust case, a bi-mode with fine particle centered at 0.2 ${\mu}m$ and coarse particle at 2 ${\mu}m$ was the characteristic size distribution in the pollution and clean cases. The different size distributions of aerosol resulted in its different optical properties. The retrieved LIDAR ratio and TDR were 41.1sr and 19.5% for a dust event, 53.8sr and 6.6% for a pollution event as well as 57.3sr and 7.2% for a clean event. In conjunction with the observed surface wind field near the LIDAR site, most of the pollution aerosols were produced locally or transported from the southeast of Beijing, whereas the dust aerosols associated with the clean air mass were transported by the northwesterly or southwesterly winds.

• Korean Journal of Optics and Photonics
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• v.32 no.6
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• pp.286-295
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• 2021

A modified catadioptric omnidirectional optical system (MCOOS) using an RGB/NIR CMOS sensor is optically designed for a capsule endoscope with the front field of view (FOV) in visible light (RGB) and side FOV in visible and near-infrared (NIR) light. The front image is captured by the front imaging lens system of the MCOOS, which consists of an additional three lenses arranged behind the secondary mirror of the catadioptric omnidirectional optical system (COOS) and the imaging lens system of the COOS. The side image is properly formed by the COOS. The Nyquist frequencies of the sensor in the RGB and NIR spectra are 90 lp/mm and 180 lp/mm, respectively. The overall length of 12 mm, F-number of 3.5, and two half-angles of front and side half FOV of 70° and 50°-120° of the MCOOS are determined by the design specifications. As a result, a spatial frequency of 154 lp/mm at a modulation transfer function (MTF) of 0.3, a depth of focus (DOF) of -0.051-+0.052 mm, and a cumulative probability of tolerance (CPT) of 99% are obtained from the COOS. Also, the spatial frequency at MTF of 170 lp/mm, DOF of -0.035-0.051 mm, and CPT of 99.9% are attained from the front-imaging lens system of the optimized MCOOS.

• Korean Journal of Optics and Photonics
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• v.20 no.4
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• pp.249-254
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• 2009

In our study, the Hanle spectrum and nonlinear magneto-optic effect (NMOE) signals were observed as a function of magnetic field on $D_1$ line of $^{87}Rb$ atoms contained in a paraffin coated vapor cell. We observed the double structure from the Hanle and the NMOE spectrum in the paraffin coated Rb vapor cell. The narrow spectral width of the narrow resonance signal is approximately 1 kHz and the magnitude is approximately 10 percent of the total spectrum. Also, the NMOE signals corresponding to the Hanle configuration consisted of two different dispersion-like features. At the near zero magnetic field, a sharp slope signal was centered, and its value was 10 mV/${\mu}T$ with laser power was $200{\mu}W$.

• Journal of Astronomy and Space Sciences
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• v.27 no.2
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• pp.153-160
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• 2010

We modified the optical system of 500 mm wide-field telescope of which point spread function showed an irregularity. The telescope has been operated for Near Earth Space Survey (NESS) located at Siding Spring Observatory (SSO) in Australia, and the optical system was brought back to Korea in January 2008. After performing a numerical simulation with the tested value of surface figure error of the primary mirror using optical design program, we found that the surface figure error of the mirror should be fabricated less than root mean square (RMS) $\lambda$/10 in order to obtain a stellar full width at half maximum (FWHM) below $28\;{\mu}m$. However, we started to figure the mirror for the target value of RMS $\lambda$/20, because system surface figure error would be increased by the error induced by the optical axis adjustment, mirror cell installation, and others. The radius of curvature of the primary mirror was 1,946 mm after the correction. Its measured surface figure error was less than RMS $\lambda$/20 on the table of polishing machine, and RMS $\lambda$/15 after installation in the primary mirror cell. A test observation performed at Daeduk Observatory at Korea Astronomy and Space Science Institute by utilizing the exiting mount, and resulted in $39.8\;{\mu}m$ of stellar FWHM. It was larger than the value from numerical simulation, and showed wing-shaped stellar image. It turned out that the measured-curvature of the secondary mirror, 1,820 mm, was not the same as the designed one, 1,795.977 mm. We fabricated the secondary mirror to the designed value, and finally obtained a stellar FWHM of $27\;{\mu}m$ after re-installation of the optical system into SSO NESS Observatory in Australia.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.345-351
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• 2014

Purpose: The accommodative response and the near horizontal phoria were examined with additional spherical power to analyze the stimulus and response AC/A ratios that suggest reference data for the binocular vision. Methods: The open-field autorefractometer (Nvision-K 5001, Shin nippon) and modified thorington method (MIM card; Muscle Imbalance Measure card, Bernell) at 40 cm were utilized to measure the accommodative response and the near horizontal phoria for 81 persons ($20.89{\pm}1.92$ years old) with additional spherical power. The stimulus and the response AC/A ratios were calculated by gradient AC/A method. Results: The exophoria group showed the highest accommodative response ($1.92{\pm}0.26D$) at 40 cm, followed by orthophoria group and esophoria group($1.72{\pm}0.26D$ and $1.62{\pm}0.42D$, respectively) Meanwhile, the esophoria group showed the biggest ocular deviation for the near ($23.24{\Delta}$) followed by the orthophoria group and exophoria group ($19.76{\Delta}$ and $15.14{\Delta}$, respectively). The biggest difference of the stimulus and the response AC/A ratios was $1.72{\Delta}$ for the exophoria group with -2.00 D, while the one was $3.43{\Delta}$ for the esophoria group with +1.00 D. There was a significant difference between AC/A ratios for the exophoria group with -2.00 D, -1.00 D and the esophoria group with +3.00 D, +2.00D, +1.00D and -1.00D. Conclusions: The difference between stimulus and response AC/A was greater when increased minus spherical power for the exophoria group, while it was greater when increased plus spherical power for the esophoria group. Furthermore, the difference for the esophoria group was a greater than the one for the exophoria group.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.147.2-148
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• 2016

Light management technology is very important for thin film solar cells, which can reduce optical reflection from the surface of thin film solar cells or enhance optical path, increasing the absorption of the incident solar light. Using proper light trapping structures in hydrogenated amorphous silicon (a-Si:H) solar cells, the thickness of absorber layers can be reduced. Instead, the internal electric field in the absorber can be strengthened, which helps to collect photon generated carriers very effectively and to reduce light-induced loss under long-term light exposure. In this work, we introduced a chemical etching technology to make honey-comb textures on glass substrates and analyzed the optical properties for the textured surface such as transmission, reflection and scattering effects. Using ray optics and finite difference time domain method (FDTD) we represented the behaviors of light waves near the etched surfaces of the glass substrates and discussed to obtain haze parameters for the different honey-comb structures. The simulation results showed that high haze values were maintained up to the long wavelength range over 700 nm, and with the proper design of the honey-comb structure, reflection or transmission of the glass substrates can be enhanced, which will be very useful for the multi-junction (tandem or triple junction) thin film a-Si:H solar cells.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.1
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• pp.72-81
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• 2015

Objectives: The aim of this study was to investigate the exposure and risk assessment of residents near asbestos mines in Korea. Methods: To assess asbestos types and airborne concentrations, air monitoring was performed in the neighborhoods of Kwangcheon (KC) and Sinsuk (SS) mines, which were leading South Korean mines in the past. In addition, activity-based-sampling (ABS) of residents' particular activities were conducted in order to estimate the Excess Lifetime Cancer Risks (ELCRs) for the residents. Conclusions: The average concentration of airborne asbestos in KC was 0.0014 f/cc and 0.0015 f/cc by PCM and TEM, respectively. In SS it was equal at 0.0012 f/cc by PCM and TEM. No statistically significant difference was found in the average concentration of airborne asbestos between the two mines. The average asbestos concentration of ABS was 0.0048 f/cc (PCM) and 0.0042 f/cc (TEM) in KC, while it was 0.0137 f/cc (PCM) and 0.0125 f/cc (TEM) in SS. It was found that the average asbestos concentration of ABS in SS was statistically significantly higher than that of KC (p<0.01). The results of ELCRs by scenario in KC showed that the scenarios of bicycle, car, weed control, weed whacking, child playing in the dirt, and physical training fell within $1{\times}0^{-6}-1{\times}10^{-4}$, which is the acceptable range of ELCR. The scenarios of motorcycle, walker, digging, and field sweeping, however, exceeded the acceptable range. In SS, only the scenario of car fell within the acceptable range, while all of the other scenarios exceeded the acceptable range.

• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.134-141
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• 1998

A high performance afocal zoom telescope has been designed to operate in the 7.6${\mu}{\textrm}{m}$ to 10.3${\mu}{\textrm}{m}$ waveband for thermal imaging system. This IR zoom telescope is characterized by using of two movable optical element groups, variator and compensator, with mechanically compensated method and the positioning of these groups is controlled by means of a computerized program. The optical performance over the entire 4:1 zoom range and $\pm$2.31~$\pm$9.36 degrees field of view is near diffraction limit while maintaining a constant F-number. The all refracting surfaces of this system except only one aspheric surface are spherical curvature and the material for the optical elements is selected Ge and ZnSe which is used for correction of chromatic aberration.

• Korean Journal of Optics and Photonics
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• v.12 no.2
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• pp.103-108
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• 2001

In this paper, we designed and made the scanned point detecting system for 3-dimensional measurement of the light emitted from plasma display panel (PDP) , and we measured and analyzed 3-dimensional light emitted from a real PDP by using this scanned point detecting system. The scanned point detecting system has a point detector with a pinhole. The light emitted from the source at the in-focus position can pass through the pinhole and be collected by detector. The light from other sources at outof-focus positions is focused at points in front of or behind the pinhole, and thus it is intercepted by the pinhole. Therefore, we can detect light information from a particular point of a PDP cell of 3-dimensional structure. We know the electric field distribution inside the PDP cell from the 3-dimensionallight intensity distribution measured by using the scanned point detecting system. As the Z axial measurement increases, the intensity of light detected increases and intensity of light detected on the inside edge of the ITa electrode is larger than outside edge of the ITa eletrode and gap of the ITa electrodes. Also, as the measurement point moves from one barrier rib to another, the detected light is weaker near to the barrier ribs than at the center between the barrier ribs. The emitted light is concentrated at the center between barrier ribs. ribs.