PURPOSES : LED based Variable Message Signs(VMS) have been widely used to inform safety messages to the drivers in advance. Legibility Distance of VMS is the most important factor to provide the safety messages to drivers in timely and effective way. However, current National Standards on legibility distance design considers letter size only even there is a difficulty to read the signs at adverse weather conditions such as heavy fog. So, this study examined the legibility issue under fog by evaluating the legibility distance with two design factors such as letter size and luminance. METHODS : Two foggy weather conditions, intermediate and heavy fog, were simulated at real-road-scale Proving Ground. Legibility distance at daytime and nighttime was evaluated by test subjects. Subjects were asked to fill the legible distance on the test sheet and statistical significant was analysed at the lab. RESULTS : The legibility distance(LD) under fog was observed only 22 to 41% of LD observed under normal weather condition at daytime, and 26 to 45% at nighttime condition. Study results showed a consistent increase in LD with higher luminance even at same letter size and vice versa conditions, However, statically significant difference between groups was only revealed when both letter size and luminance level increased conditions. In order to apply the test results in terms of engineering benefits, LD results from significantly different groups was evaluated with relative to Stopping Sight Distance(SSD) within conceptual frame suggested in this study. CONCLUSIONS : From the study results, current National Standard on legibility distance design needs to consider letter size and luminance simultaneously to response the legibility issue in adverse weather conditions.

PURPOSES : Aiming to evaluate the consistency of road markings at night, the luminance values of road markings at night were compared for merging and diverging areas. METHODS : To evaluate the consistency of road marking at nighttime in merging and diverging areas, the highway geometric structures and luminance of the road markings were collected and analyzed together at the merging and diverging areas. "Luminance" in this study referred to the overall luminance of the road markings as reflected together from surrounding lights, such as moonlight or artificial lights. The luminance of the road markings 90 m ahead of the driver were used. The measured luminance values were analyzed based on the difference ratios and an analysis of variance. RESULTS : Based on a grouping of three categories (interchanges (ICs), merging, and diverging areas), it was found that the difference ratios and analysis of variance values from the ICs and merging and diverging areas were not consistently acceptable. CONCLUSIONS : After evaluating the consistency of road markings at night in the merging and diverging areas, it can be concluded that there is a need for more consistency in the luminance on merging and diverging areas on highways. To enhance consistency, more dedicated lighting guidance for merging and diverging areas on highway areas may be necessary.

PURPOSES : In this study, the luminance of night road markings was measured in a tunnel of length 200 m or less. The purpose of the project is to evaluate the consistency of night road markings. METHODS : In this study, field measurements were conducted to achieve the purpose of this study. Five tunnels with lengths of less than 200 m were selected to measure the luminance value of the road markings. The analysis of the difference in road markings between the inside and outside points of the tunnel and the analysis of alternative tunnels and points were used to assess the consistency of road markings in tunnels. RESULTS : The average luminance of the tunnel’s night road markings was 9.7, and the standard deviation was 3.0. The analysis of variance for the tunnel and point indicated that the p-value was less than 0.05 and was inconsistent. CONCLUSIONS : In conclusion, consistency was assessed by measuring the luminance value of the short tunnel of length 200 m in the Cheongju Sangju Expressway, and it was confirmed that the luminance of the road markings was not consistent with the tunnel and point. Finally, it is necessary to control night lightings on roads outside the tunnel or adjust lighting facilities in the tunnel to enhance the consistency of luminance.

In this study, We studied design method to reduce scattering reflection by adding a three - dimensional structure to light guide plate of LED backlight widely used in small and portable devices. In order to improve the efficiency of the light-incident part, a three-dimensional structure is used in which a repetitive structure of a prism shape and a semi-cylindrical shape is repeatedly added to the light-entering face in light-guide plate. As a result of the study, it was found that uniform luminance values were obtained in the light-incident portion and the backlight when a repetitive pattern of a semi-cylindrical shape was added as compared with a case in which a prism shape was added. Particularly, when a rectangular lens with a semi-cylindrical shape is added, the average value of the total luminance is increased by about 15% from 7278 lm to 8324 lm as compared with a general light guide plate.

디스플레이의 화질은 중요한 성능 지표이며, 균일도는 화질을 결정하는 주요 요소들 중의 하나이다. LED 매트릭 스 디스플레이 같이 화소마다 휘도 및 색역이 다른 경우, 디스플레이 휘도 및 컬러 균일도 개선을 위한 보정 작업이 수행되어야 한다. 적용의 편리성 때문에 대부분의 경우에 균일도 보정 방법은 모든 화소의 휘도 및 색역 중 가장 낮은 값 으로 보정을 수행하는 방식으로 진행되어왔다. 하지만, 이와 같은 방법은 균일도 보정 후 디스플레이의 휘도 및 색역이 너무 많이 감소하는 단점을 갖는다. 휘도 및 색역 감소량을 최소화하는 방법의 대안은 디스플레이가 균일하게 인지되는 범위를 도출한 후, 해당 범위 내에서 휘도 및 색역이 최대가 되는 값을 기준으로 디스플레이를 보정하는 것이다. 본 논 문에서는 이와 같은 디스플레이 균일도 보정 범위를 도출하는 방법을 제안한다. 제안하는 방법은 시각 실험을 통하여 화소간 휘도 및 색의 차이가 사람의 눈에 상이하게 인지되는 기준을 도출하고, 실험 결과를 사용하여 디스플레이 균일 도 보정 범위를 정량화 한다. 제안하는 방법의 성능은 시각 실험을 통하여 검증된다. 실험을 통해 제안하는 방법이 90% 이상의 높은 정확도로 균일도 보정 범위를 정확하게 도출하는 것을 확인할 수 있었다.

OBJECTIVES : Visibility at night can be improved by using retroreflection for short distances and phosphorescent line markings for long distances. In this study, we analyzed the characteristics of the phosphorescent line marking through a laboratory luminance test. Field performance analysis was performed through tests conducted on the road. We also examined the luminance measurement methods using the digital image obtained during the phosphorescent visibility evaluation. METHODS : In this study, the laboratory luminance test of the phosphorescent line marking was conducted using seven specimens to characterize the luminance changes according to the type of the glass beads, the thickness of the phosphorescent line marking, and the brightness and irradiation time of the light source. Phosphorescent and general line markings were made at 150 m to investigate the field luminance performance. A preliminary review of the luminance measurement methods was made using a digital image from a digital singlelens reflex (DSLR) camera. The measured luminance ratio of the general and the phosphorescent line markings was compared with the calculated luminance ratio using luminance analysis. RESULTS: Through the laboratory luminance test, it was seen that the change in luminance, which corresponds to the brightness of the light source, appears large but the influence of the thickness and irradiation time is low. The field performance test of the phosphorescent line marking conducted on the road involved measuring the luminance on the day the marking was made and 7 days after the marking was made. The luminance was found to be 190 mcd/m2 at 30 min after sunset and approximately 10-12 mcd/m2 4h after sunset. The results of the luminance test were captured using a digital image for each time group. The luminance ratio of the phosphorescent line marking, when compared to that of the general line marking, showed a similar trend within a 13% maximum error. Additionally, when this luminance ratio is compared to the direct field measurement, it could be confirmed that the luminance ratio, as captured in the digital image, showed a similar tendency. CONCLUSIONS : 1) The change in luminance corresponding to the brightness of the light source is significant in comparison with that corresponding to the thickness and the irradiation time. In addition, the results of the field test for the phosphorescent line marking satisfied the phosphorescent fire protection standard. 2) We examined the validity of the luminance measurement method using a digital image and we concluded that the change in the luminance ratio shows a similar tendency in both the cases. The results can form the basis for luminance measurement methodology for the construction and maintenance of phosphorescent line markings.

OBJECTIVES : A fog generated field test was conducted to analyze the relationship between the luminance of variable speed-limit signs and the legibility distance under various fog density conditions. By using this study, appropriate luminance values can be selected depending on the density of fog. METHODS: An actual tunnel was selected as the area to conduct the test, as other places cannot maintain the fog condition because of rapid air current. Ninety-two subjects were recruited for this test, which took place during the course of three days. Visibility-distance detecting sensor was used to measure the visibility distance due to the fog density time, simultaneously with the evaluation of legibility distance by subjects. RESULTS: The test results show the relationship between luminance values and the legibility distance corresponding to the visibility distance due to fog. According to the technical test results, lower luminance value such as 7000 cd/m2 corresponds to less legibility distance compared to higher values such as 20000 cd/m2 or 40000 cd/m2. However, the amount of difference between 20000 cd/m2 and 40000 cd/m2 is negligible in our test. CONCLUSIONS: The results of this study can be used to select appropriate luminance of valuable speed signs under fog conditions. Hence, drivers can expect to have more room to respond to adverse weather conditions, thereby reducing the risk of accidents.

White organic light-emitting diodes with a structure of indium-tin-oxide [ITO]/ N,N-diphenyl-N,N-bis-[4-(phenylm- tolvlamino)-phenyl]-biphenyl-4,4-diamine [DNTPD]/ [2,3-f:2, 2-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile [HATCN]/ 1,1- bis(di-4-poly-aminophenyl) cyclo -hexane [TAPC]/ emission layers doped with three color dopants/ 4,7-diphenyl-1,10- phenanthroline [Bphen]/ Cs2CO3/ Al were fabricated and evaluated. In the emission layer [EML], N,N-dicarbazolyl-3,5-benzene [mCP] was used as a single host and bis(2-phenyl quinolinato)-acetylacetonate iridium(III) [Ir(pq)2acac]/ fac-tris(2- phenylpyridinato) iridium(III) [Ir(ppy)3]/ iridium(III) bis[(4,6-di-fluoropheny)-pyridinato-N,C2] picolinate [FIrpic] were used as red/green/blue dopants, respectively. The fabricated devices were divided into five types (D1, D2, D3, D4, D5) according to the structure of the emission layer. The electroluminescence spectra showed three peak emissions at the wavelengths of blue (472~473 nm), green (495~500 nm), and red (589~595 nm). Among the fabricated devices, the device of D1 doped in a mixed fashion with a single emission layer showed the highest values of luminance and quantum efficiency at the given voltage. However, the emission color of D1 was not pure white but orange, with Commission Internationale de L'Eclairage [CIE] coordinates of (x = 0.41~0.45, y = 0.41) depending on the applied voltages. On the other hand, device D5, with a double emission layer of mCP:[Ir(pq)2acac(3%) +Ir(ppy)3(0.5%)]/ mCP:[FIrpic(10%)], showed a nearly pure white color with CIE coordinates of (x = 0.34~0.35, y = 0.35~0.37) under applied voltage in the range of 6~10 V. The luminance and quantum efficiency of D5 were 17,160 cd/m2 and 3.8% at 10 V, respectively.

PURPOSES: This study aimed to evaluate the appropriateness of safety with the standard for threshold zone luminance as specified in the Recommendation for Lighting of Traffic Tunnel, which has been widely adopted worldwide. METHODS: A driving test of the subject in a full-scale road tunnel was conducted. The adaptation luminance and threshold zone luminance, which should be known for the driver to perceive an object within stopping sight distance, were obtained. These values were compared with the adaptation luminance and threshold zone luminance obtained by the existing reduced model test and tunnel lighting standard that has served as a guideline for the current threshold zone luminance standard. RESULTS : According to this study, threshold zone luminance should be increased to at least 1.8 times the value proposed in the existing studies and to twice the domestic tunnel lighting standard (KS C 3703: 2014). CONCLUSIONS : The threshold zone luminance proposed in this study differs largely from that obtained from indoor tests and from the current tunnel lighting standard used worldwide; this difference may be attributed to the fact that the indoor tests did not incorporate driving workload, non-uniformity of luminance distribution in terms of sight, and factors that reduce the visibility of the driver, such as the light reflected into the driver’s eyes. Hence, it is necessary to further review the factors that reduce the visibility of drivers approaching tunnels in order to determine the rational tunnel threshold zone luminance.

PURPOSES : The purpose of this study is to suggest a basis for setting appropriate safety goals specifically related to the threshold zone luminance in a vehicular traffic tunnel. . METHODS: In the test, drivers were divided into two groups. One group consisted of all drivers (average drivers) group with an age ratio of drivers holding domestic driver's license and driver group by age to produce threshold zone luminance in the tunnel. The threshold zone luminance produced as a result was used to analyze how it affects the safety level of each driver group and provide a basis for setting an appropriate safety criterion that can be used to determine threshold zone luminance. We used test equipment, test conditions, and ananalysis of threshold zone luminance identical to that reported by ChoandJung(2014) but the values of adaptation luminance in our analys is were expanded to range from100 to10,000 cd/m2. RESULTS : Adaptation luminance and threshold zone luminance are found to be related by a quadratic function. The threshold zone luminance needed by older drivers to ensure a certain safety level is significantly higher than that for drivers of other age brackets when adaptation luminance increases. 56% of older drivers are at an increased risk of an accident at the same luminance for which the safety level of average drivers is 75%. The safety level that can be achieved for older drivers increases to above 60% when threshold zone luminance level is set with the goal of attaining a safety level of more than 85% for average drivers. The safety level that can be attained for average drivers is above 90% when the threshold zone luminance is high enough to ensure over 75% in the safety level of older drivers. Results of this study are applicable to highways and others whose designed speed is 100 km/h. CONCLUSIONS : Threshold zone luminance determined on the basis of drivers having average visual ability is of limited value as a performance standard for ensuring the safety of older drivers. Hence, safety level for older drivers should be considered separately from safety levels for drivers with an average ability to avoid risk. Upward adjustment of older drivers' safety level in the process of determining appropriate threshold zone luminance in a vehicular traffic tunnel may bring both tangible and intangible benefit as a result of reducing accidents. However, there is an associated dollar cost arising from installing and operating lights. As a result, the economic impact of these trade-offs should also be considered.

2009년 아이폰의 국내 출시 이후 스마트폰의 보급이 급격히 증가하여 기존에 다양한 장비로 수행되어 오던 작 업이 스마트폰으로 대체되었다. 이 과정에서 스마트폰의 작은 화면을 통하여 글자를 읽는 과제를 수행하는 비중 이 상당히 증가하였다. 본 연구에서는 일상적인 스마트폰 사용 환경에서 디스플레이 요인(화소 밀집도, 화소 하부구조, 휘도)과 환경 요인(조명 조도)이 글자를 읽을 때의 가독성 관련 불편감에 어떤 영향을 미치는지를 확인 하였다. 그 결과 지각된 가독성 관련 불편감에 영향을 미치는 것은 주로 화소 밀집도로, 화소 밀집도가 300 PPI 미만인 경우 글자를 읽는데 불편함을 느낀다는 것을 확인하였다. 조명 조도는 제한적인 영향을 보였다. 참가자들은 조명 조도가 변화 할 때 변화하지 않을 때 보다 더 큰 가독성 관련 불편감을 보고하였다. 화소 하부구조와 밝기는 가독성 관련 불편감에 영향을 미치지 않았다. 이 결과를 바탕으로 가독성을 고려할 때 다양한 크기를 가지는 스마트 기기(스마트 폰, 태블릿 컴퓨터)에서 가독성을 해치지 않는 해상도의 하한선을 제안하였다.

PURPOSES : This study has been performed with the objective to determine threshold zone luminance of adaptation luminance by target safety level in a vehicular traffic tunnel with design speed set at 100km/h . METHODS: The study made a miniature capable of portraying changes in luminance distribution within 2×10。conical field of view of the driver approaching to the tunnel for the test. Test conditions were set based on justifications for CIE 88-1990's threshold zone luminance used as a reference by domestic tunnel light standards (KS C 3703 : 2010). Luminance contrast of object background and object is 23%, object presentation duration is 0.5 seconds, and size of the object background is 7.3×11.5m2 RESULTS: Threshold zone luminance was set within adaptation luminance of 100~3,000cd/m2. Adaptation luminance and threshold zone luminance based on 50%, 75% and 90% target safety level all showed a relatively high linear relationship. According to findings in the study, it is not appropriate to specify the relationship between adaptation luminance and threshold zone luminance as luminance ratio. Rather, direct utilization of the linear relationship gained from the study findings appears to be the better solution. CONCLUSIONS : Findings of this study may be used to determine operation of threshold zone luminance based on target safety level. However, a proper verification and validity of test results are required. Furthermore, a study to determine proper threshold zone luminance level considering target safety level reviewed in this study and various decision-making factors such as economic conditions in Korea and energyrelated policies should be carried out in addition. Additional tests on adaptation luminance greater than 3,000cd/m2 will be performed, through which application scope of the test findings will be broadened.

목 적: 크로마젠 렌즈의 색상별 시감투과율과 색상에 따른 근거리 시력과 선명도를 측정하여 비교 연구하기 위함이다. 방 법: 8가지 색상을 가진 크로마젠 렌즈의 분광투과율을 Shimadzu사의 UV-VIS Spectrophotometer(UV-2450)를 사용하여 측정한 후 380~780nm의 가시광선 전 영역에 대한 시감투과율을 구하였다. 대전 소재 K대학교 대학생 중에서 원거리 양안 교정시력이 1.0이상이 나오는 학생 총 30명 대상으로 800lux의 조명에서 40cm 근거리용 스넬렌 E시표를 이용하여 색상별 근거리 시력을 측정하고 가장 선명도가 좋은 색상과 가장 선명도가 떨어지는 색상을 선택하여 색상별 분포를 알아보았다. 결 과: 시감투과율은 Yellow 69.9%, Blue 69.1%, Violet 68.4%, Pink 63.5%, Aqua Blue 63.2%, Orange 61.5%, Magenta 52.2%, Green 46.2% 로 나타났다. 크로마젠 렌즈를 착용한 상태에서 Yellow와 Blue에서 가장 높은 시력이 측정되었고, Green과 Magenta에서 가장 낮은 시력이 측정되었다. 선명도가 가장 높은 색상으로는 Blue(30%)가 가장 많이 선택되었고, 선명도가 가장 낮은 색상으로는 Magenta(26.7%)로 많이 선택되었다. 결 론: 시감투과율이 높은 색상일수록 근거리 시력과 선명도가 우수하였다. 따라서 렌즈의 색상 선택 시시감투과율이 시력에 미치는 영향을 반드시 고려해야 할 것이다. 색상의 비교 분석에 따라 적절한 색상을 선택해야 한다.

YAG:Ce yellow phosphor particles were synthesized by spray pyrolysis with changing the solution properties and their luminous properties, crystal structure, and morphological changes were studied by using PL measurement, XRD, and SEM analysis. It was clear that the solution properties significantly affected the crystal phase, crystallite size, the PL intensity, and the morphology of YAG:Ce particles. At low calcination temperature, the addition of urea only to the spray solution was helpful to form a pure YAG phase without any impurity phases, as the result, the highest luminescence intensity was achieved at the calcination temperature of . When the calcination temperatures were larger than , however, the YAG particles prepared without any additive showed the highest luminescent intensity. Regardless of the solution conditions, the emission intensity of YAG:Ce particles prepared by spray pyrolysis showed a linear relation with the crystallite size. In terms of the morphology of YAG:Ce particles, the addition of both DCCA and to the spray solution was effective to prepare a spherical and dense structured YAG particles.

We have seen the effects of buffer layer in organic light-emitting diodes(OLEDs) using poly(N-vinylcarbazole)(PVK) depending on a concentration of PVK. Polymer PVK buffer layer was made using spin casting technique. Two device structures were fabricated; one is ITO/TPD/Alq3/Al as a reference, and the other is ITO/PVK/TPD/Alq3/Al to see the effects of buffer layer in organic light-emitting diodes. Current-voltage-luminance characteristics and an external quantum efficiency were measured with a variation of spin-casting rpm speeds and PVK concentration. We have obtained an improvement of external quantum efficiency by a factor of four when the PVK concentration is 0.1wt% is used. The improvement of efficiency is expected due to a function of hole-blocking of PVK in OLEDs.

본 연구의 목적은 기존의 고상 반응법을 이용하여 일본의 상용 Zn2SiO4:Mn형광체보다 우수한 성능의 형광체를 제조하는데 있다. 이틀 위해 본 연구에서는 고상 반응법을 이용하여 Zn2SiO4:Mn 형광체를 합성하고, 이를 PDP(Plasma Display Panel)에 적용하기 위하여 소성온도 및 환원 온도와 주입되는 기체의 양, dopant Mn의 농도를 다양하게 하여 합성하였고, ball milling 등을 통하여 입자의 특성을 개선하는 실험을 하였다. 제조된 형광체의 발광특성 및 모양 등의 특성은 상용 Zn2SiO4:Mn 형광체와 비교하였다. Mn의 농도를 0.08mo1e로 하여 1300˚C에서 소성하였을 때 결정성 및 휘도가 가장 우수하였고, 환원시 5% H2-96% N, 혼합가스의 양을 100ml/rnin으로 일정하게 주입시켰을 때 20%이상 휘도가 증가하였다. Ball rnilling은 30분 동안 100rpm으로 하였을 때 입자의 크기가 수십 μm에서 3μm이하로 줄어들었다. 특히. 발광 특성이 상용 형광체보다 월등히 우수하여 PDP에 적용할 수 있다

최근 교통 표지판, 차막이 등 여러 안전시설물 등에 시인성을 겸비한 재료를 이용하여 발광기능 뿐만 아니라 유도기능을 부여하는 사례가 많이 늘고 있다. 그러나 이러한 발광재료의 무문별한 과다사용은 인간의 시선을 방해할 수도 있다. 그러므로 인지 가능한 최소한의 빛의 밝기를 확보함과 동시에 사용 목적에 맞는 적절한 발광재료 또는 발광재료의 배치를 적용할 필요가 있다. 본 논문에서는 인간이 인지할 수 있는 최소한의 빛의 광도를 측정하기 위해 여러 단계의 밝기에 따른 휘도(조사면적당 광도, cd/m2)를 측정하였다. 이에 대해 인간이 인지 가능한 임계휘도 값을 도출하고, 이 값에 대한 신뢰성을 갖기 위해 불특정다수의 인간을 대상으로 검증 실험을 수행하였다.

최근 교통 표지판, 차막이 등 여러 안전시설물 등에 시인성을 겸비한 재료를 이용하여 발광기능 뿐만 아니라 유도기능을 부여하는 사례가 많이 늘고 있다. 그러나 이러한 발광재료의 무분별한 과다사용은 인간의 시선을 방해할 수도 있다. 그러므로 인지 가능한 최소한의 빛의 밝기를 확보함과 동시에 사용 목적에 맞는 적절한 발광재료 또는 발광재료의 배치를 적용할 필요성이 있다. 본 논문에서는 인간이 인지할 수 있는 최소한의 빛의 광도를 측정하기 위해 휘도(조사면적당 광도, cd/m2) 측정기를 사용하여 휘도를 측정하였다. 광원에서 15m 떨어진 거리에서 주황색과 파랑색 두 가지 색에 대한 인지 가능여부 실험을 수행하였다.