• Journal of Korean Society for Atmospheric Environment
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• v.27 no.2
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• pp.201-208
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• 2011

Recently, a real-time, pocket-sized aethalometer (microAeth$^{(R)}$ model AE51) has been developed by Magee Scientific Inc. for measuring the concentration of black carbon in the atmosphere. In this study, two aethalometers, models AE-16 and AE-51, which measure the optical absorption of carbon particles at infrared 880 nm, were operated at time interval of 5-min between January 9 and February 10, 2010 at an urban site of Gwangju, to compare the accuracy of black carbon (BC) concentrations reported from the AE-51 model and to investigate reasonable sampling time of filter media in the AE-51. The air samples in the AE-51 and AE-16 models are collected on T60 (Teflon coated glass fiber) filter media (filter spot area: 0.07 $cm^2$) and quartz fiber roll-tape filter (filter spot area: 1.67 $cm^2$), respectively. Real-time measurement results indicate that when the filters were clean, the AE-51 BC was greater than or similar to the AE-16 BC data. However as the filter spots become darker, the AE-16 BC concentrations were higher than the AE-51 BC data and the difference in the BC concentrations from two AE models becomes gradually increased. Relative error in the AE-51 and AE-16 BC concentrations showed significance difference depending on used time of the filter in the AE-51 model, weather pattern, levels of air pollution, etc, ranging from 11.5% (used time of the filter in AE-51: 1,595 min) to 52.5% (used time of the filter in AE-51: 2,085 min). When considering the used time of one filter ticket in the AE-51 model and difference (or relative error %) between AE-16 and AE-51 BC concentrations, it is recommended that the standard sampling time per one filter ticket within the AE-51 model be less than approximately 24 hr (1,440 min) under the normal weather conditions except for severe haze and mist events.

• Journal of the Semiconductor & Display Technology
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• v.20 no.1
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• pp.77-82
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• 2021

Using a multi-array needle module developed for coating of high-density cylindrical microlens array (C-MLA), we have fabricated an anti-Moiré filter for LED screens. The Moiré phenomenon appears due to the interference between the array pattern of image sensors in a camera and the non-emission area (grid pattern) of a LED screen. To suppress it, we have employed poly(methyl methacrylate) (PMMA) and coated it on a glass substrate in the form of a grid and non-grid (parallel lines). We have rotated the needle module in order to increase the number of C-MLAs. With this scheme, we have fabricated the 150 mm × 150 mm anti-Moiré filters where 836 microlens lines are formed. They show the average width of 255.4 ㎛, the average distance between CMLs of 94.6 ㎛, and C-MLA width non-uniformity of 4.7%. We have shown that the Moiré patterns still appear in the presence of the parallel (non-grid)-type filter, whereas they disappeared completely by the grid-type filter. It is due to the fact that the Moiré patterns are diffused more effectively by the grid-type C-MLA.

• Journal of Sensor Science and Technology
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• v.30 no.4
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• pp.250-254
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• 2021

A highly sensitive and selective non-dispersive infrared (NDIR) carbon dioxide gas sensor requires achieving high transmittance and narrow full width at half maximum (FWHM), which depends on the interface of the optical filter for precise measurement of carbon dioxide concentration. This paper presents the design, simulation, and fabrication of a Fabry-Perot filter based on a distributed Bragg reflector (DBR) for a low-cost NDIR carbon dioxide sensor. The Fabry-Perot filter consists of upper and lower DBR pairs, which comprise multilayered stacks of alternating high- and low-index thin films, and a cavity layer for the resonance of incident light. As the number of DBR pairs inside the reflector increases, the FWHM of the transmitted light becomes narrower, but the transmittance of light decreases substantially. Therefore, it is essential to analyze the relationship between the FWHM and transmittance according to the number of DBR pairs. The DBR is made of silicon and silicon dioxide by RF magnetron sputtering on a glass wafer. After the optimal conditions based on simulation results were realized, the DBR exhibited a light transmittance of 38.5% at 4.26 ㎛ and an FWHM of 158 nm. The improved results substantiate the advantages of the low-cost and minimized process compared to expensive commercial filters.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.70-77
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• 2010

This study proposed an auto focusing method for a multi-focus image in assembling lens modules in digital camera phones. A camera module in a camera phone is composed of a lens barrel, an IR glass, a lens mount, a PCB board and aspheric lenses. Alignment among the components is one of the important factors in product quality. Auto-focus is essential to adjust image quality of an IR glass in a lens holder, but there are two focal points in the captured image due to thickness of IR glass. So, sharpness, probability and a scale factor are defined to find desired focus from a multi-focus image. The sharpness is defined as clarity of an image. Probability and a scale factors are calculated using pattern matching with a registered image. The presented algorithm was applied to a lens assembly machine which has 5 axes, two vacuum chucks and an inspection system. The desired focus can be determined on the local maximum of the sharpness, the probability and the scale factor in the experiment.

• Journal of the Korean Wood Science and Technology
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• v.35 no.4
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• pp.61-66
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• 2007

The study was performed to purify and characterize laccase in culture of Trametes versicolor. The fungus was grown in liquid culture media of PDB and added 2,5-xylidine (0.2 mM) after 5 days to enhance the production of laccase. The fungal culture was incubated at $25^{\circ}C$ on a rotary shaker (120 rpm) for 7days, and the culture broth was clarified through Glass filter (GF/C). The aqueous solution was concentrated by ultramicrofiltration (Viva flow 50, GE Healthcare Bioscience, USA) and loaded onto a Hitrap Q FF column. Laccase activity could be detected at one peak, and this enzyme has a molecular mass of approximately 53kDa as determined by SDS-PAGE The optimum pH and temperature for syringaldazine were 5.0 and $60^{\circ}C$, respectively. The specific activity of crude, concentrated and purified laccase were 32, 409, and 1,243 U/mg, respectively.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.783-787
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• 2004

Microwave dielectric properties and the microstructure of $Ba_5Nb_4O_{15}$ ceramics with $PbO-B_2O_3-SiO_2$ glass frit were investigated to reduce the sintering temperature of $Ba_5Nb_4O_{15}$ ceramics as a function of the amount of glass frit from $0.5wt\%$ to $10wt\%$ and the sintering condition. The sintered density and the microwave dielectric properties of $Ba_5Nb_4O_{15}$ ceramics were remarkably changed with the amount of glass fit which existed as a liquid phase and assisted the densification. $Ba_5Nb_4O_{15}$ with $3wt\%$ $PbO-B_2O_3-SiO_2$ glass frit sintered at $900^{\circ}C$ for 2 h showed dielectric constant (K) of 41.4, a quality factor (Q $\times$f) of 13,485 GHz, and a Temperature Coefficient of resonant Frequency (TCF) of 9 ppm/$^{\circ}C$. Due to no trace of physical and chemical reaction between this composition and Ag electrode cofired at $900^{\circ}C$ for 2 h, this ceramics can be a good candidate for the multilayer dielectric filter.

• Korean Journal of Materials Research
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• v.4 no.7
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• pp.783-791
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• 1994

Piezoelectric ZnO thin films were deposited on 7059 glass substrate by rf magnetron sputtering. The effects of deposition parameter, such as rf power, gas pressure and $O_{2}$/Ar gas ratio, on the crystallinity and electrical properties of the deposited ZnO thin films were studied. It was found that the deposition rate was higher than the previously reported values. ZnO films were suitable for SAW filter since a standard deviation of XRD (002) peak rocking curve was less than $6^{\circ}$. ZnO thin films, which were deposited at $O_{2}$/Ar ratio larger than 25%, showed high resistance. SAW filter was fabricated using ZnO film, of which thickness was 0.25 of the wavelength of the propatating surface acoustic wave. The measured frequency response was consistent with the calculated one. The SAW filter had center frequency 39.08 MHz, phase velocity 2501 m/sec and insertion loss 29 dB.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.4
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• pp.357-362
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• 2011

Purpose: The narrow-band pass color-filters with a 500 nm central wavelength and 12 nm FWHM using $Ti_3O_5/SiO_2$ mutilayer were fabricated, and their characteristics and structures were studied. Methods: the optical constants, n and k, of the $Ti_3O_5$ and $SiO_2$ thin films were obtained from the transmittances of their thin film. The narrow-band pass color-filters were designed with these optical constants and the AR coating of the filter was also designed. $Ti_3O_5/SiO_2$ multilayer filters were made by electron beam evaporation apparatus and the transmittaces of the filters were measured by spectrophotometer. the number of layers and the thicknesses of filters were calculated from the cross section of filters by SEM image and the composition of filters was analysed by XPS analysis. Results: The optimization of AR coating for the narrow-band pass color-filter was [air$|SiO_2(90)|Ti_3O_5(36)|SiO_2(5)|Ti_3O_5(73)|SiO_2(30)|Ti_3O_5(15)|$ glass], and the optimization of filter layer for the color filter was [air$|SiO_2(192)|Ti_3O_5(64)|SiO_2(102)|Ti_3O_5(66)|SiO_2(112)|Ti_3O_5(74)|SiO_2(120)|Ti_3O_5(68)|SiO_2(123)|Ti_3O_5(80)|SiO_2(109)|Ti_3O_5(70)|SiO_2(105)|Ti_3O_5(62)|SiO_2(99)|Ti_3O_5(63)|SiO_2(98)|Ti_3O_5(51)|SiO_2(60)|Ti_3O_5(42)|SiO_2(113)|Ti_3O_5(88)|SiO_2(116)|Ti_3O_5(68)|SiO_2(89)|Ti_3O_5(49)|SiO_2(77)|Ti_3O_5(48)|SiO_2(84)|Ti_3O_5(51)|SiO_2(85)|Ti_3O_5(48)|SiO_2(59)|Ti_3O_5(34)|SiO_2(71)|Ti_3O_5(44)|SiO_2(65)|Ti_3O_5(45)|SiO_2(81)|Ti_3O_5(52)|SiO_2(88)|$ glass]. It was known that the color-filters fabricated by the simulation data were composed of 41 layers by SEM image and the top layer of filters was $SiO_2$ layer and the filters were composed of $SiO_2$/$Ti_3O_5$ multilayer by XPS analysis. It was also known that the mixed thin film of TiO2 and $Ti_3O_5$ was made during the deposition of the $Ti_3O_5$ material. Conclusions: The narrow-band pass color-filters with a 500 nm central wavelength and 12 nm FWHM using $Ti_3O_5/SiO_2$ mutilayer of 41 layer were fabricated, and it was known that the mixed form of TiO2 and $Ti_3O_5$ thin film was made during the deposition of the $Ti_3O_5$ material.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.27-36
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• 2019

The demand for a low dispersion lens with a small refractive index and a high refractive index is increasing, and accordingly, there is an increasing need for a releasable protective film with high heat resistance and abrasion resistance. On the other hand, the optical industry has not yet established a clear standard for the manufacturing process and quality standards for mold-releasing protective films used in aspheric glass lens molding. Optical lens manufacturers treat this technology as proprietary information. In this study, an experiment was conducted regarding the optimization of ion etching, magnetron, and arc current at each source and filter part, and bias voltage in FCVA (filtered cathode vacuum arc)-based Ta-C thin film coatings. This study found that compared to iridium-rhenium alloy thin film sputtering products, the coating conditions were improved by approximately 50%, 20%, and 40% in terms of thickness, hardness, and adhesive strength of the film, respectively. The thin-film coating process proposed in this study is expected to contribute significantly to the development and utilization of glass lenses, which will help enhance the minimum mechanical properties and quality of the mold-release thin film layer required for glass mold surface forming technology.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.857-860
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• 2002

The material that is both conductive in electricity and transparent to the visible-ray is called transparent conducting thin film. It has many field of application such as solar cell, liquid crystal display, transparent electrical heater, selective optical filter, and a optical electric device. In this study, indium tin oxide (ITO ; Sn-doped $In_2O_3$) thin films were deposited on $SiO_2$/soda-lime glass plates by a dc magnetron sputtering technique. The crystallinity and electrical properties of the films were investigated by X-ray diffraction(XRD), atomic force microscopy (AFM) scanning and 4-point probe. The optical transmittance of ITO films in the range of 300-1000nm were measured with a spectrophotometer. As a result, we obtained polycrystalline structured ITO films with (222), (400), and (440) peak. Transmittance of all the films were higher than 90% in the visible range.