• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.61-68
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• 2010

Optical simulation methods were applied to the edge-lit LED backlight for LCD TV applications in order to optimize the optical structure of the light guide plate(LGP), and thus to improve the uniformity properties by removing the bright spots caused by LED's. The edge-lit LED backlight consisted of three white LED's with a lamp cover, a light guide plate, and a reflection film. When there was no pattern on the entrance side surface of the LGP, the illuminance uniformity was sensitively dependent on the distance d between the LED and the entrance surface. The illuminance uniformity increased with d but its increasing rate slowed down when d was beyond ~ 1.5 mm. When micro-patterns such as a lenticular lens array (LLA) or a serration pattern were formed on the entrance surface, the illuminance uniformity was improved substantially even for the case of very small d. At the same simulation condition, the lightguide with serration pattern showed a better uniformity than that with LLA pattern. Additional improvement could be achieved by changing the refractive index of the micro-patterns. These results suggest that using micro-patterns is a very effective way to reduce the bright spots due to their refracting function for the concentrated incident rays onto the LGP.

• The Korean Journal of Vision Science
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• v.20 no.4
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• pp.579-588
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• 2018

Purpose : To analyze the eyeglasses supply system for ametropic soldiers in ROK military. Methods : We investigated and analyzed the supply system of eyeglasses for the ametropic soldiers provided by the Korean military. The refractive powers and corrected visual acuity were measured for 37 ametropic soldiers who wear insert glasses for ballistic protective and gas-masks supplied by the military based on their habitual prescriptions. Full correction of refractive error was prescribed for subjects having less than 1.0 of distance visual acuity, and comparison was held for inspecting the changes in corrected visual acuity. Suggestions were provided for solving the issues regarding current supplying system, and this study investigated the applicabilities for utilizing professional optometric manpower. Results : The new glasses supplied by army for ametropic soldiers were duplicated from the glasses they worn when entering the army. The spherical equivalent refractive powers of the conventional, ballistic protective and gas-mask insert glasses supplied for 37 ametropic soldiers were $-3.47{\pm}1.69D$, $-3.52{\pm}1.66D$ and $-3.55{\pm}1.63D$, respectively, and the spherical equivalent refractive power of full corrected glasses was $-3.79{\pm}1.66D$, which showed a significant difference(p<0.05). The distant corrected visual acuity measured at high and low contrast(logMAR) of conventional, ballistic protective and gas-mask insert glasses were $0.06{\pm}0.80$, $0.21{\pm}0.82$, $0.15{\pm}0.74$, $0.34{\pm}0.89$, $0.10{\pm}0.70$ and $0.22{\pm}0.27$, respectively, while the corrected visual acuity by full corrected glasses were increased to $0.02{\pm}1.05$, $0.10{\pm}0.07$, $0.09{\pm}0.92$, $0.26{\pm}0.10$, $0.04{\pm}1.00$ and $0.19{\pm}1.00$, respectively. There was a significant difference(p<0.05) except for the case of the low contrast corrected visual acuity of the conventional and gas-mask insert glasses. The procedure for ordering, dispensing, and supplying military glasses consists of 5 steps, and it was found that approximately two weeks or more are required to supply from the initial examination. Conclusion : The procedure of supplying the military glasses showed three issues: 1) a lack of refraction for prescription system, 2) relatively long length of time required for supplying the glasses, 3) an inaccurate power of supplied glasses. In order to solve those issues, in the short term, education is necessarily required for soldiers on the measurement of the refractive powers, and in the near future, further standard procedures for prescription of glasses as well as the securement of optometric manpower are expected.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.46-46
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• 2000

과학기술 및 산업의 발달로 인하여 실험 중 또는 공정 상에서 in situ, 실시간으로 측정하고 분석하며 이를 되먹임하는 품질제어의 중요성이 대두되고 있다. 반도체 공정 또는 박막제조 공정 중에서 박막의 두께, 굴절율, 물질의 조성비 등을 알아내는 것이 긴요한 과제로 대두되고 있으며, 이를 위하여 공정중인 제품의 품질을 실시간으로 평가하는 장비가 요구되고 있는 것이다. 나아가 공정중의 예상하지 못한 시료의 특성변화를 그대로 감지하여 적절히 보정해 주는 되먹임 기법은 높은 수율을 보장하는 첨단기법이라 할 수 있다. 이러한요구에 부응할 수 있는 본 제품(Elli-situ 2000)은 박막의 두께 표면변화를 sub 의 정밀도를 가지고 in situ, 실시간으로 정밀 측정할 수 있는 첨단 계측장비로서 빛의 편광상태 변화를 측정하기 때문에 공정 중의 시료에 영향을 주지 않는 비간섭 특성과 비접촉 특성의 장점 뿐만 아니라 공기중에서는 물론 진공이나 액체 등의 매질에서도 사용될 수 있어서 매질에 대한 제약이 거의 없다는 장점도 가지고 있다. 편광상태의 제어 및 측정을 필요한 광학장비의 경우, 제작이 까다롭기 때문에 대부분 가격이 높은 편이고 사용방법이나 측정 데이터에 대한 해석이 어렵다는 단점이 있으나, Elli-situ 2000의 경우 상용화된 외국제품(국내제품은 없슴)과 비교하여 성능 및 가격경쟁력에 있어서도 우위에 있으며 간단, 명료한 장비조작 및 컴퓨터를 사용한 구동의 전자동화를 이룸으로써 초보자도 쉽게 측정하고 데이터를 처리할 수 있도록 하였다. 또한 취부대의 경우, 진공포트 플랜지의 표준규격(2-3" Del-Seal 플랜지 규격)에 맞춤으로써 기존의 진공챔버에 부착하여 진공에 전혀 영향을 주지 않는 상태에서 시료의 변화를 in situ, 실시간으로 정밀 측정할 수 있도록 하였다. 하였다.O 박막은 산소 가스압력과 기판온도, 인가 전류를 변화시켜가며 증착하였으며 이에 따른 박막의 결정성 변화를 알아보았다. 기판온도를 실온에서 점차 증가시켜나가면 $\Delta$$\theta$50은 급격히 감소하며 30$0^{\circ}C$에서는 결정성이 우수한 막을 얻을 수 있었다. 또한 산소 가스 압력이 0.5~1mTorr에서 $\Delta$$\theta$50은 양호한 값을 나타내었지만 그 이상에서는 c-축 배향성이 나빠짐을 확인하였다. 따라서 대향타겟식스퍼터 장치를 이용하여 ZnO 박막을 증착시 가스압력 0.5~1mTorr, 기판온도 20$0^{\circ}C$이상의 막 제작조건에서 결정성이 우수하게 나타나는 것을 확인할 수 있었다. gluten이 단단해졌음을 알수 있었다. 유화제 stearly 칼슘, 혹은 hemicellulase를 amarans 10% 대체한 밀가루에 첨가하면 확연히 비용적을 증대시킬 수 있다는 사실을 알 수 있었다. quinoa는 명아주과 Chenopodium에 속하고 페루, 볼리비아 등의 고산지에서 재배 되어지는 것을 시료로 사용하였다. quinoa 분말은 중량의 5-20%을 quinoa를 대체하고 더욱이 분말중량에 대하여 0-200ppm의 lipase를 lipid(밀가루의 2-3배)에 대하여 품질개량제로서 이용했다. 그 결과 quinoa 대량 7.5%에서 비용적, gas cell이 가장 긍정적 결과를 산출했고 반죽의 조직구조가 강화되었다. 또 quinoa 대체에 의해 전분-지질 복합제의 흡열량이 증대된 것으로부터 전분-지질복합제의 형성 촉진이 시사되었다.이것으로 인하여 호화억제에 의한 노화 방지효과가 기대되었지만 실제로 빵의 노화는 현저히 진행되었다. 이것은

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.1
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• pp.19-24
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• 1995

Large size potassium lithium niobate (KLN) crystals with dimensions of $8{\times}6{\times}2 mm^3$ were grown by the top - seeded solution growth (TSSG) method. The extraordinary refractive index $n_e$at the second harmonic frequency for KLN crystal depends on the composition and decreases in this crystal due to the large Li content. KLN crystal was characterized by observation in UV - VIS spectrometry. It is transparent from the ultraviolet to infrared spectral regions that the transmission limit and cut- off wavelength are about 350 and 380 nm.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.106-106
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• 2000

반도체 소자가 미세화 됨에 따라 게이트 유전막으로 사용되는 SiO2의 박막화가 요구되나, boron penetration에 의한 Vt shift, 게이트 누설전류, 다결정 실리콘 게이트의 depletion effect 그리고 quantum mechanical effect 때문에 ~20 급에서 한계를 나타내고 있다. 이에 0.1$\mu\textrm{m}$이상의 design rule을 갖는 logic이나 memory 소자에서 요구되어지는 ~10 급 게이트 산화막은 SiO2(K=3.9)를 대신하여 고유전율을 갖는 재료의 채택이 필수 불가결하게 되었다. 고유전 박막 재료를 사용하면, 두께를 두껍게 해도 동일한 inversion 특성이 유지되고 carrier tunneling 이 덜하여 등가 산화막의 두께를 줄일 수 있다. 이러한 고유전박막 재료중 가장 활발히 연구되고 있는 재료는 Ta2O5, Al2O3, STO 그리고 BST 등이 있으나 Ta2O5, STO, BST 등은 실리콘 기판과 직접 반응을 한다는 문제를 가지고 있으며, Al2O3는 유전율이 낮의 재료가 최근 주목받고 있다. 본 실험에서는 ZrO2, HfO2 또는 그 silicates 등의 재료가 최근 주목 받고 있다. 본 실험에서는 ZrO2 박막의 증착조건에 따른 물리적, 전기적 특성 변화에 대하여 연구하였다. RCA 방식으로 세정한 P-type (100) 실리콘 기판위에 reactive DC sputtering 방법으로 압력 5mtorr, power 100~400W, 기판온도는 100-50$0^{\circ}C$로 변화시켜 ZrO2 박막을 증착한 후 산소와 아르곤 분위기에서 400-80$0^{\circ}C$, 10-120min으로 열처리하였다. 증착직후의 시편들과 열처리한 ZrO2 박막의 미세구조와 전기적 특성 변화를 관찰하였다. 우선 굴절율(RI)를 이용해 ZrO2 박막의 밀도를 예측하여 power와 기판온도에 따라 이론값 2.0-2.2 에 근접한 구조를 얻은 후 XRD, XPS, AFM, 그리고 TEM을 사용하여 ZrO2 박막의 chemical bonding, surface roughness 그리고 interfacial layer의 특성을 관찰하였다. 그리고 C-V, I-V measurement를 이용해 capacitance, 유전율, 누설전류 등의 전기적 특성을 관찰해 최적 조건을 설정하였다.

• Korean Journal of Optics and Photonics
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• v.19 no.3
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• pp.224-228
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• 2008

A highly sensitive integrated photonic temperature sensor was proposed and developed incorporating a polymeric microring resonator. The change in the ambient temperature was estimated by observing the shift in the resonant wavelength of the resonator induced via the thermooptic effect. For the purpose of enhancing its sensitivity, the sensor was built by implementing a polymeric resonator exhibiting a high thermooptic coefficient on a silicon substrate with a small coefficient of thermal expansion. For the range of from $20^{\circ}C$ to $30^{\circ}C$ near the room temperature, the fabricated sensor yielded a sensitivity of as high as 165 ${\pm}/^{\circ}C$ and a resolution of better than $0.1^{\circ}C$. And its performance was found to be hardly affected by the variation in the refractive index of the target analyte, which was applied to the surface of the sensor. It is hence expected that the sensor could be integrated with other refractormetric optical sensors, thereby compensating for the fatal error caused by the change in the ambient temperature.

• Fire Science and Engineering
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• v.29 no.3
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• pp.59-64
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• 2015

This study analyzed results of the causes of failure in 1,022 fire trucks currently being used in South Korea (aerial ladder, aerial platform, pumper, and chemical fire trucks). The results show that 46% of aerial ladder trucks have defective in the elevator brake systems, 29% of aerial platform trucks have contamination in the hydraulic oil, 37% of pumpers have defective in the pneumatic cylinders of the air supply system, and 39% of chemical fire trucks have defective in the powder fire extinguishing systems. The principal reasons for malfunctions are deterioration of the apparatuses, and accumulated fatigue from repetitive use of certain components, such as pneumatic cylinders in the air supply system and wire rope jamming in rollers in the ladder apparatus. These manufacturing defects should be improved upon in the manufacturing process. As a result, the fire trucks, which are used for 5 years or more, need precise inspections in accordance with the Regulation on Fire Apparatus Maintenance. Fire apparatuses have a service life of 10 to 12 years or more. They need to be replaced or require life extension, and they should be kept in top shape with the best maintenance for public safety.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.2
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• pp.59-64
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• 2000

We performed refraction, keratometry, slit lamp biomicroscopy. We selected 58 current spherical RGP lens wearers for this three-month study. All patients exhibits at least 0.75D of corneal astigmatism measured with the keratometer, and 37 patients had corneal astigmatism of 1.50D or greater. At least follow-up visit, we measured Snellen acuity with lenses, and performed overrefraction, overkeratometry and slit lamp biomicroscopy. We charted lens position, movement and surface quality. During the three month, biomicroscopy revealed no corneal edema and neovascularization on any patients. Fluorescein staining were 52 patients case of grade 0.5 patients case of grade 1, and 1 patient case of grade 2. In evaluating post-fit residual cylinder, on overrefraction as a percentage of refractive cylinder. By the initial visit, one-week visit, one-month visit, and two-month visit are 41%, 34%, 29%, respectively. In this data, we knew no change after one month. The average overrefraction for these eyes in absolute diopters is 0.26D(initial visit), 0.22D(one-week visit, 0.17D(one-month visit), and 0.16D(two-month visit). The use of a regimen containing a dedicated daily cleaner was more effective in maintaining patient comfort and lens cleanliness than was the use of a regimen containing only a multipurpose solution.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.2
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• pp.239-246
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• 2014

Purpose: This study was performed to investigate the effect of induced ametropia on static posture for body balance. Methods: Twenty subjects (10 males, 10 females) of average age $23.4{pm}2.70$ years were participated and ametropia(binocular myopia; BM, simple myopic anisometropia; SMA, binocular hyperopia; BH, and simple hyperopic anisometropia; SHA) were induced with ${pm}0.50D$, ${\pm}1.00D$, ${\pm}1.50D$, ${\pm}2.00D$, ${\pm}3.00D$, ${\pm}4.00D$, ${\pm}5.00D$, respectively. General stability (ST), weight distribution index (WDI), and fall risk index (FI) were measured using TETRAX the biofeedback systems. Each index of the body balance was evaluated for 32 seconds in each ametropic condition and those value was compared with the value in fully corrected condition. Results: The ST showed significant increase from +0.50 D under condition of BM, from +1.00 D under condition of SMA, from -1.00 D under condition of BH, and from -1.50 D under condition of SHA compared with under condition of fully corrected condition, respectively. The FI showed significant increases from +4.00 D under condition of BM, from -1.00 D under condition of BH, and from -1.50 D under condition of SHA. The WDI show no change in all ametropia condition. Conclusions: Whatever ametropia is, uncorrected refractive error could reduce the general stability of body balance and increase the falling risk.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.459-465
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• 1993

By making the inter-metal PECVD $SiO_2$ as a Si rich oxide under the SOG, the hydrogen and water related diffusants could be captured a t SI dangling bonds. This gettering process was known to prevent the device characteristics degradations related to the H, $H_20$. The basic characteristics of Si rich oxide have been studied according to changing high/low frequency power and $SiH_4/N_2O$ gas flow ratio in PECVD. As increase in low frequency power, deposition rate decreased but K.I. and compressive stress increased. Decrease of the water peaks of FTIR spectra at the wave number range of 3300~3800$\textrm{cm}^{-1}$' also indicated that intensty the films were densified. As increase in SiH, gas flow rate, deposition rate, R.I. and etch rate increased while compressive stress decreased. F'TIK spectra showed that peak intensity corresponding to Si-0-Si stretching vibration decreased and shifted to the lower wave numbers. But AES showed that Si dangl~ng bonds were increased as a result of lower Si:O(l: 1.23) ratlo inthe Si rich oxide as compared to Si : O(1 : 1.98) ratio of usual oxide.