• Korean Journal of Optics and Photonics
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• v.16 no.3
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• pp.254-260
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• 2005

By incorporating large core polymer waveguides, which have been developed for increased alignment tolerance in passive fiber attachment, highly efficient variable optical attenuators are proposed. In order to find optimum device structures, 3-dimensional beam propagation method (BPM) simulations are performed. Heat distribution over the polymer film is calculated to find the 3-dimensional index profile data for the BPM simulation. Due to the small index contrast between the core and cladding materials in the large core waveguide, heat-induced radiation occurs for small heating power. While the ordinary VOA needs the temperature to change over $150^{\circ}C$ for 20 dB attenuation, the large core VOA requires only $70^{\circ}C$. In addition to the merit of passive fiber attachment, the proposed VOA has enhanced attenuation efficiency for the lower temperature change.

• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.384-389
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• 2002

A new idea of the wavelength locking module for DWDM application was investigated in the present research. Only one etalon photo-diode is generally used in the internal/external wavelength locking system. For the internal wavelength locking module with 50 GHz applications, an algle tuning method of the etalon commonly applied. However, the alignment process of the etalon with the angle tuning method is limited because the lock performance is extremely sensitive accoriding to the change of the tilting angle. In an optical viewpoint, the alignment tolerance of the locker module with the etalon PD array block was good, and the precise tuning of the wavelength was possible. The characteristics of free spectral range (FSR) and peak shift of wavelength according to the tilting angle with the locker module was investigated. For the present module, the optimized initial tilting angle was experimentally obtained.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.36.2-36.2
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• 2010

The CQUEAN (Camera for QUasars in EArly uNiverse) is an optical CCD camera optimized for observation of high redshift objects. It is going to be attached to the cassegrain focus of 2.1m telescope at McDonald Observatory, USA. We are making a focal reducer for CQUEAN to secure a larger field of view. The focal reducer is composed of four spherical lens, and it reduces the focal length of telescope by one third. We designed the lens configuration, performed tolerance analysis, and estimated the optical performance with ZEMAX. The differences in optical performace with/without filters were also investigated. The result from ZEMAX shows that the system has ample margin of errors for median seeing of 1.2" at McDonald observatory. Even with aberration and alignment tolerance, the performance is better than the original requirement. The lenses are now being made, and the lens barrel and an adapter for assembly of the Andor CCD camera and the filter wheel is now under designing process. We expect that the manufacturing of the focal reducer system as well as its optical test will be finished by April 2010.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.153.2-153.2
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• 2011

The IGRINS (Immersion GRating INfrared Spectrometer) is a high resolution wide-band infrared spectrograph developed by Korea Astronomy and Space Science Institute (KASI) and the University of Texas at Austin (UT). Immersion grating is a key component of IGRINS, which disperses the input ray by using a Silicon material with a lithography technology. Opto-mechanical mount for the immersion grating is important to keep the high spectral resolution and the optical alignment in a cold temperature of $130{\pm}0.06K$. The optical performance of immersion grating can maintain within the de-center tolerance of ${\pm}0.05mm$ and the tip-tilt tolerance of ${\pm}1.5arcmin$. The mount mechanism utilizes the flexure and the kinematic support design to satisfy the requirement and the operation condition. When the IGRINS system is cooled down to a cold temperature, three flexures compensate the thermal contraction stress due to the different material between the immersion grating and the mounting part(Aluminum 6061). They also support the immersion grating by an appropriate preload. Thermal stability is controlled by a copper strap with proper dimensions and a heater. Generally structural and thermal analysis was performed to confirm the mount mechanism. This talk presents the opto-mechanical mount design of the immersion grating of IGRINS.

• The Journal of Korean Society for Radiation Therapy
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• v.16 no.2
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• pp.43-61
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• 2004

Purpose : For qualify improvement in radiotherapy, it is important to set up and evaluate equipment (linac) accurately. In addition, technicians are needed to be fully aware of the equipment's detailed quality and its manual. Therefore, the result of ATP is evaluated and introduced, in order that the technicians are skilled by participating in quality assurance (QA) and understanding the quality of the equipment before clinical use. Method and Material : QA for LINAC 21EX (Varian, US) was done with suppliers its procedure was divided into radiation survey, mechanical test, radiation isocenter test, bean performance, dosimetry, and enhanced dynamic wedge and using X-omat film (Kodak), multidata, densitometer, and electrometer. QA of MLC (Millennium, 120 leaf) attached to LINAC and EPID (Portal vision) were done separately. Result : The leakage dose by survey meter was below the tolerance. In mechanical test, collimater, gantry, and couch rotation were less than 1mm, and the angles were ${\pm}0.1^{\circ}$ for digital and ${\pm}0.5^{\circ}$ for mechanical. The alignment test of the light field and crosshair were evaluated less than 1mm. The (a)symmetrical jaw field was less than ${\pm}0.5mm$. The radiation isocenter test using X-mat film was less than 1mm. The consistency of light field and radiation field was less than ${\pm}0.1mm$. PDD for photon energy was less than ${\pm}1\%$ and for electron energy of $90\%,\;80\%,\;50\%,\;and\;30\%$ were evaluated within the tolerance. Flatness for photon and electron energy was evaluated $2.3\%$ (tolerance $3\%$) and $3\%$ (tolerance $4.5\%$), respectively, and symmetry was $0.45\%$ (tolerance $2\%$) and $0.3\%$ (tolerance $2\%$), respectively. Dosimetry test for short term, MU setting, rep rate, and dose rate accuracy of photon and electron energy was within the tolerance depending on energy, MU, and gantry angle. Conclusion : Accuracy and safety for clinical use of Clinac 21EX was verified through customer acceptance procedure and the quality of the equipment was found out. These can reduce the difficulties in using the equipment. Furthermore, it is useful for clinically treatment of patients by technicians' active participations.

• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.440-445
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• 2005

The limitation of measurement accuracy and reliability of autostigmatic null lens system are studied for the cases of using inter-distance of null lenses as the adjustment factor of alignment and fixing the distance by mounting. If we investigate the first case, the wavefront aberration of null lens system is compensated by the adjustment process even though the shape of aspherical surface is not properly fabricated. As the result, it brings about the problem of measurement reliability. However, for the fixing process by mounting null lenses, it doesn't cause the reliability problem because the wavefront aberration of null lens system is not compensated. Further, the fixing process shows nearly same result in measurement accuracy to the adjustment process, that is, $0.0316{\lambda}$ vs. $0.0326{\lambda}$. So, we can conclude the setup for autostigmatic null lens system must be constituted by means of the fixing process. Meanwhile, we introduce and define the alignment aperture on aspheircal mirror, which can be approximated as spherical zone for alignment of null lens system, and besides, we calculate the required fabrication accuracy of the zone for the necessary measurement accuracy.

• International Journal of Industrial Entomology and Biomaterials
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• v.15 no.2
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• pp.123-130
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• 2007

The Hsp 20.8 and Hsp 90 cDNA sequence retrieved from NCBI database and consists of 764 bp and 2582 bp lengths respectively. The corresponding cDNA homologus sequences were BLAST searched in Bombyx mori genomic DNA database and two genomic contigs viz., BAAB01120347 and AADK01011786 showed maximum homology. In B. mori Hsp 20.8 and Hsp 90 is encoded by single gene without intron. Specific primers were used to amplify the Hsp 20.8 gene and Hsp 90 variable region from genomic DNA by using the PCR. Obtained products were 216 bp in Hsp 20.8 and 437 bp in Hsp 90. There was no variation found in the six silkworm races PCR products size of contrasting response to thermal tolerance. The comparison of the sequenced nucleotide variations through multiple sequence alignment analysis of Hsp 90 variable region products of three races not showed any differences respect to their thermotolerance and formed the clusters among the voltinism. The comparison of aminoacid sequences of B. mori Hsps with dipteran and other insect taxa revealed high percentage of identity growing with phylogenetic relatedness of species. The conserved domains of B. mori Hsps predicted, in which the Hsp 20.8 possesses ${\alpha}-crystallin$ domain and Hsp 90 holds HATPase and Hsp 90 domains.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.62.2-62.2
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• 2010

The CQUEAN (Camera for QUasars in EArly uNiverse) is an optical CCD camera optimized for the observation of high redshift QSOs to understand the nature of early universe. The focal reducer, which is composed of four spherical lens, is allowed to secure a wider field of view for CQUEAN, by reducing the focal length of the system by one third. We designed the lens configuration, the lens barrel, and the adapters to assemble to attach focal reducer to the CCD camera system. We performed tolerance analysis using ZEMAX. The manufacturing of the focal reducer system and its lab test of optical performance were already finished. It turned out that the performance can meet the original requirement, with the aberration and alignment error taken into account. We successfully attached the focal reducer and CQUEAN to the cassegrain focus of 2.1m telescope at McDonald Observatory, USA, and several tests of CQUEAN system were carried out. In this presentation, I will show the process of focal reducer fabrication and the result of performance test.

• Journal of Power Electronics
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• v.18 no.1
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• pp.277-288
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• 2018

Wireless inductive power transfer (IPT) technology is used in many applications today. A compact and high-frequency primary side inverter is one of the most important parts of a WPT system. In this study, a modified class EF-type voltage-fed multi-resonant inverter has been proposed for WPT application at a frequency range of 85-100 kHz. Instead of an infinite input choke inductor, a resonant inductor is used to reduce loss and power density. The peak voltage stress across the MOSFET has been reduced to almost 60% from a class-E inverter using a passive clamping circuit. A simple yet effective design procedure has been presented to calculate the various component values of the proposed inverter. The overall system is simulated using MATLAB/SimPowerSystem to verify the theoretical concepts. A 500-W prototype was built and tested to validate the simulated results. The inverter exhibited 90% efficiency at nearly perfect alignment condition, and efficiency reduced gradually with the misalignment of WPT coils. The proposed inverter maintains zero-voltage switching (ZVS) during considerable load changes and possesses all the inherent advantages of class E-type inverters.

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.511-518
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• 2004

Providing marine signal lanterns with advantages of little weight as well as large aperture, a Fresnel lens has been adopted to transfer the beam from the lanterns up to 10 nautical miles (18.53 km). A Fresnel lens with the diameter of 250 mm and 300 mm was designed by a lens design program and optimized by adjusting the groove parameters of the lens. The angular luminous intensity distribution (ALID) of this lens was calculated by using an illumination analysis program considering the ALID of a light bulb. At the best alignment of the bulb, the maximum luminous intensities (MLI) of the lantern were 1000 cd (in the case of 250 mm diameter) and 1300 cd (in the case of 300 mm diameter). These are more than the critical value of 720 cd that is the Korean Standard of MLI for the marine lantern. The ALID was investigated as a function of misalignment from the lens focus to determine the tolerance of the alignment ranges.