• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.67.3-68
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• 2020

A prime focus telescope, e.g., Schmidt telescope, has advantages especially for a wide field of view survey in astronomy. In this optical configuration, the camera is placed in front of the primary mirror. Since the installation of a typical filter wheel to the prime focus telescope causes serious obscuration of the incoming light, a customized filter device is required for high sensitivity images. In this poster, we present a new filter exchange mechanism, which can host four filters moving along quadrant directions. We plan to install this on the Celestron 36 cm Rowe-Ackermann Schmidt Astrograph (RASA 36) located at El Sause Observatory in Chile.

• Publications of The Korean Astronomical Society
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• v.20 no.1 s.24
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• pp.143-149
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• 2005

KASI (Korea Astronomy and Space Science Institute) is developing the near-infrared camera system named KASINICS (KASI Near-Infrared Camera System) which will be installed at the 60cm f/13.5 Ritchey-Chretien telescope of the Sobaeksan Optical Astronomy Observatory (SOAO). The camera system is optimized for JHKL bands and has a 6 arcmin FOV. The optical system consists of two spherical mirrors and a 8-position filter wheel. With the exception for the dewar window, all optical elements are cooled inside cryogenic dewar. Since the Offner system is adopted to prevent thermal noises from outside of the telescope primary mirror, the secondary mirror of the Offner system acts as a cold Lyot stop. The optical performance does not change by temperature variations because the Aluminum mirrors contract and expand homogeneously with its mount. We finished the design and fabrication of the optical parts and are now aligning the optical system. We plan to have a test observation on 2006 January.

• Journal of radiological science and technology
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• v.28 no.4
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• pp.327-332
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• 2005

The purpose of this Study was to investigate the prevalence rate of idiopathic scoliosis to the students from the elementary to the university in S city of Chung-Nam using 100 mm Mirror Camera radiation indirect examination units, with on age range of between eight and thirteen (1.526 subjects), fourteen and sixteen (462 subjects), seventeen and eighteen (291 subjects), nineteen and twenty four(508 subjects) and total of 2,787 participants with the 590 male subjects and 2,197 female subjects. The results of this study can be summarized and compared the primary examination with the secondary test of greater than $10^{\circ}$of Cobb's Angle were obtained as follows; 1. Indirect Examination were conducted to find idiopathic scoliosis amomg total 2.787 subjects, 257 subjects (9.2%) who showed positive sign greater than $10^{\circ}$in the Cobb's Angle ; below age of thirteen (132 subjects), between fourteen and sixteen (52 subjects), seventeen and eighteen (35 subjects), nineteen and twenty four (38 subjects). The $x^2-test$ analysis of Indirect Examination showed no statistical significant difference association between the age range and $10^{\circ}$Cobb's Angle of spinal curve(P>0.059). 2. The numbers of idiopathic scoliosis of greater than $10^{\circ}$Cobb's Angle of spinal curve in the primary examination were observed in 147 subjects (57.2%) at the Thoracolumbar region, 81subjects (31.5%) at the Thoracic region, 20 subjects (7.8%) at the Cervicothoracic region, 7 subjects (2.7%) at the Lumbar region, 2 subjects (0.8%) at the Cervical region. So, the large numbers were Thoracolumbar region, 183 participants (71.2%) showed the right side curve of scoliosis and 74 participant (28.8%) showed the left side curve of scoliosis. 3. The main region of the pain in one's own self more than $10^{\circ}$ Cobb's angle of spinal curve were no pain 219 subjects (85.2%), 18 subjects (7.0%) at the Lumbar region, 9 subjects (3.5%) at the Cervical region, 7 subjects (2.7%) at the Thoracic region, 2 subjects (0.7%) at the shoulder girdle region, 1 subjects (0.39%) at the pelvis and whole body region. There was statistical significant difference association between the Cobb's Angle of spinal curve and the main pain region of one's (P<0.006). This study may be significant to an early stage investigate of the prevalence rate of idiopathic scoliosis in the juveniles using 100 mm Mirror Camera radiation indirect examination units. The results of this study help that the students in a stage on growth the basis of data early discovery and therapy of idiopathic scoliosis.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.417-428
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• 2004

We have investigated the optical property of the KAO(Korea Astronomy Observatory) wide field telescope (named NEOPAT-3; Near Earth Object and Satellite Patrol-3) and aligned optical system. The NEOPAT-3 is restricted to V,R,I-filters because of the refractive property of the correcting lens system. Because of the fast focal ratio, the optical performance of the NEOPAT-3 is very sensitive to its alignment factors of the optical system. To make the spot radius smaller than $8{\mu}m$ in rms over 2degree${\times}2$degree field, the optical system must satisfy the following conditions: 1) The tilt error between detector plane and focal plane should be less than 0.05degree. 2) The decenter error between the primary mirror and the correcting lens system should be less than 1mm. 3) The distance error between the primary mirror and the correcting lens system should be less than 2.3mm. In order to align the optical system accurately, we measured the aberrations of the telescope quantitatively by means of curvature sensing technique. NEOPAT-3 is installed temporary on the roof of the TRAO(Taeduk Radio Astronomy Observatory) main building to normalize system performance and to develop automatic observation.

• Ocean and Polar Research
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• v.30 no.4
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• pp.407-418
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• 2008

Seawater samples were collected at discrete depths from five stations across the polar front in the Drake Passage (Antarctic Ocean) by the $20^{th}$ Korea Antarctic Research Program in December, 2006. Nitrate concentrations of seawater increase with depth within the photic zone above the depth of Upper Circumpolar Deep Water (UCDW). In contrast, ${\delta}^{15}N$ values of seawater nitrate decrease with depth, showing a mirror image to the nitrate variation. Such a distinct vertical variation is mainly attributed to the degree of nitrate assimilation by phytoplankton as well as organic matter degradation of sinking particles within the surface layer. The preferential $^{14}{NO_3}^-$ assimilation by the phytoplankton causes $^{15}{NO_3}^-$ concentration to become high in a closedsystem surface-water environment during the primary production, whereas more $^{14}{NO_3}^-$ is added to the seawater during the degradation of sinking organic particles. The water-mass mixing seems to play an important role in the alteration of ${\delta}^{15}N$ values in the deep layer below the UCDW. Across the polar front, nitrate concentrations of surface seawater decrease and corresponding ${\delta}^{15}N$ values increase northward, which is likely due to the degree of nitrate utilization during the primary production. Based on the Rayleigh model, the calculated ${\varepsilon}$ (isotope effect of nitrate uptake) values between 4.0%o and 5.8%o were validated by the previously reported data, although the preformed ${\delta}^{15}{{NO_3}^-}_{initial}$ value of UCDW is important in the calculation of ${\varepsilon}$ values.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.51-57
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• 2001

A light beam reflected from a machined surface generally containes information concerning about its surface roughness. This study examines and proposes a surface roughness measurement technique for on-machine measurement of machined surfaces. The technique is based on the measurement of a reflected laser beam pattern and the statistical analysis of its light intensity distribution. The surface roughness was found to be closely related to the standard deviation of the light intensity on the primary axis of the reflected pattern. An image acquisition device is made up of a laser diode, a half mirror, a screen, and a CCD camera. The exact image with the primary and secondary axes of a reflected laser beam pattern is calculated through such image processing algorithm as thresholding, edge detection, image rotation, segmentation, etc. A median filter and a surrounding light correction algorithm are improve the image quality and reduce the measuring error. Using the developed measuring device the effect of screen materials and workpiece and workpiece materials was investigated. Experimental results regarding to relatively high-quality surfaces machined by grinding, polishing, lapping processes have shown the measurement error is within 10% in the range of $0.1{mu}m~0.8{\mu}m R_q.$Therefore, the proposed method is thought to be effectively used when quick measurements is needed with workpieces fixed on the machine.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.521-526
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• 2005

We assembled the optical beam director with diameter 300 mm. This consists of primary, secondary mirrors and 5 folding mirrors. Among them, the primary mirror is the most important component so that we measure any possible deformation on it at every step of assembly. Also, we developed the systematic alignment algorithm, which is essential because the number of mirrors is 7. The final wavefront error of the system is 1.9 wave rms (wave=633 nm) which is 7 times larger than we expected. The main source is the deformation of the 131ding mirrors. We expect that what we have learned from the assembly of this system would be helpful when we deal with a larger system in the future.

• Publications of The Korean Astronomical Society
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• v.32 no.1
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• pp.343-345
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• 2017

We present the development of a spectral dispersion device for wideband spectroscopy for which the primary scientific objective is the characterization of transiting exoplanets. The principle of the disperser is simple: a grating is fabricated on the surface of a prism. The direction of the spectral dispersion power of the prism is crossed with the grating. Thus, the prism separates the spectrum into individual orders while the grating produces a spectrum for each order. In this work, ZnS was selected as the material for the cross disperser, which was designed to cover the wavelength region, ${\lambda}=0.6-13{\mu}m$, with a spectral resolving power, $R{\geq}50$. A disperser was fabricated, and an evaluation of its surface was conducted. Two spectrometer designs, one adopting ZnS (${\lambda}=0.6-13{\mu}m$, $R{\geq}300$) and the other adopting CdZnTe (${\lambda}=1-23{\mu}m$, $R{\geq}250$), are presented. The spectrometers, each of which has no moving mechanical parts, consist simply of a disperser, a focusing mirror, and a detector.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2415-2420
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• 2002

In the present study, a new anchor design was proposed to minimize the initial deflection of micro multi-layer cantilever beam with step-up structure, which is a key component of thin film micro-mirror array. It is important to minimize the initial deflection, caused by residual stress, because it reduces the performance of the actuation. Theoretical and experimental studies were conducted to examine the cause of the initial bending deflection. It was found that the bending deflection at the anchor of the cantilever beam was the primary source of initial deflection. Various anchor designs were proposed and the initial deflections for each design were calculated by finite element analysis. The analysis results were compared with experiments. To reduce the initial deflection a secondary support was added to the conventional structure. The optimal shapes were obtained by simulation and experiment. It was found from the analysis that the ratio or horizontal and vertical dimensions of secondary support was the governing factor, which affected the initial deflection.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.40-45
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• 2004

Recently, aspheric optical lenses and mirrors, which are harder to manufacture and measure than the conventional spherical ones, are widely used, particularly in electronic fabrication process. Generally, interferometric optical method is used for the measurement of spherical optical surface. However, the interferometric method for aspheric surface measurement is difficult because it needs a precise null corrector and strict environmental conditions such as constant temperature, humidity and vibrations. We have been studied on the manufacturing of aspheric optics to improve the surface profile accuracy and productivity using a corrective polishing process. For the corrective polishing, a practical method of On-Machine Measurement (OMM) is required. For this purpose, an optical OMM system has been studied using the Shach-Hartmann test, which is very robust to the practical polishing environment. The wavefront has been reconstructed from the measured data using the primary aberration polynomial function by the least squares fitting. The measured result of the OMM system shows that the maximum deviation is less than 200 nm for the one of commercial Fizeau interferometer Wyko 6000.