• Current Optics and Photonics
• /
• v.1 no.4
• /
• pp.389-395
• /
• 2017

This paper investigates a method to improve the lighting performance of white light-emitting diodes (WLEDs), which are packaged using two separate remote phosphor layers, a yellow-emitting YAG:Ce phosphor layer and a red-emitting ${\alpha}-SrO{\cdot}3B_2O_3:Sm^{2+}$ phosphor layer. The thicknesses of these two layers are $800{\mu}m$ and $200{\mu}m$, respectively. Both of them are examined in conditions where the average correlated color temperatures (CCT) are 7700 K and 8500 K. For this two-layer model, the concentration of red phosphor is varied from 2% to 30% in the upper layer, while in the lower layer the yellow phosphor concentration is kept at 15%. It was found interestingly that the lighting properties such as color rendering index (CRI) and luminous flux are enhanced significantly, while the color uniformity is maintained in a relatively close range to the one of one-layer configuration (measured at the same correlated color temperature). Besides, the transmitted and reflected light of each phosphor layer are revised by combining Kubelka-Munk and Mie-Lorenz theories. Through analysis, it is demonstrated that the packaging configuration of two-layer remote phosphor that employs red-emitting ${\alpha}-SrO{\cdot}3B_2O_3:Sm^{2+}$ phosphor particles provides a practical solution for general WLEDs lighting.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.43 no.2 s.308
• /
• pp.33-39
• /
• 2006

This paper designed the electronic circuit part of Potable Infrared Night Vision Scope for a small size, light weight, and low power. Designed electronic circuit part is composed of an Auto Voltage Selecting Module, and a Power Supply Module. An Auto Voltage Selecting Modulo is composed of a switch, a battery, a step up voltage part, and a selecting voltage part. A Power Supply Module is composed of a high luminous sensing part, a battery voltage sensing part, a infrared illumination part, a connection sensing part, and a power control part. And this module controls the power of Image Intensifier Tube. To verify the performance of the designed electronic circuit part, we experimented the consumption power and continuous using time. Experimental results show that the designed electronic circuit part improves considerably on the performance of the AN/PVS-14. performance.

• KIEAE Journal
• /
• v.3 no.2
• /
• pp.45-50
• /
• 2003

Today, there are increasing evidences that daylight is essential for health, well-being and productivity. One of the strong contributions, which atria can make to advantages in building, is in allowing the use of daylight. This research is to develop nomographs and to evaluate the daylight performances of toplit atria with louvers. For this purpose, the evaluation models of toplit atria with well indexes of 0.5, 1.0 or 2.0 have been selected through the field surveys of atrium buildings in Seoul area. Also, weather data for solar irradiance and luminous efficacy were gathered from the recently conducted previous researches. The computer simulations were performed under clear sky conditions, using the ADELINE program, and various daylight performances were analyzed by the daylight illumination ratio. Analyzing the simulation results, solar altitude, solar azimuth, and louver angle and louver reflectance were found to be important factors affecting the daylight performance of toplit atria. Using these variables, regression equations have been formulated, and the nomographs, which may predict the daylight performances of toplit atria with louvers, were developed. The developed nomographs were validated through comparing the results of nomograph predictions to the results of scale-model experiments.

• Journal of the Korean Solar Energy Society
• /
• v.24 no.2
• /
• pp.39-50
• /
• 2004

One of the challenge for successful daylighting design might be to capture sunlighting that varies in both intensity and position and to deliver the luminous flux into the inner space as deep as possible. Conventional glazing apertures allow daylight in the outer 3.5m of a perimeter spaces. More advanced daylighting technologies can extend this daylighting depth by reflecting sunlight further from the windows within a deep floor area. For this purpose, this study developed light shelves based on performance evaluation with a mock-up model that constructed recently and measured under real sky condition. All these daylighting devices have a customized geometry developed from the solar path at a given latitude and utilize unique reflecting finishing to maximize the amount of redirection and diffusion of the daylight. This paper tells that the best daylighting penetration typically can be expected from using light-colored sloped external shelves.

• Current Optics and Photonics
• /
• v.2 no.2
• /
• pp.153-164
• /
• 2018

In semiconductor manufacturing, critical dimensions indicate the features of patterns formed by the semiconductor process. The purpose of measuring critical dimensions is to confirm whether patterns are made as intended. The deposition process for an organic light emitting diode (OLED) forms a luminous organic layer on the thin-film transistor electrode. The position of this organic layer greatly affects the luminescent performance of an OLED. Thus, a system for measuring the position of the organic layer from outside of the vacuum chamber in real-time is desired for monitoring the deposition process. Typically, imaging from large stand-off distances results in low spatial resolution because of diffraction blur, and it is difficult to attain an adequate industrial-level measurement. The proposed method offers a new superresolution single-image using a conversion formula between two different optical systems obtained by a deep learning technique. This formula converts an image measured at long distance and with low-resolution optics into one image as if it were measured with high-resolution optics. The performance of this method is evaluated with various samples in terms of spatial resolution and measurement performance.

• Journal of Sensor Science and Technology
• /
• v.31 no.4
• /
• pp.238-243
• /
• 2022

In this study, a pyrene-core single molecule with amino (-NH₂) functional group material was hybridized using ZnO quantum dots (QDs). The suppressed performance of the 1-aminopyrene (1-PyNH₂) single molecule as an emissive layer (EML) in light-emitting diodes (LEDs) was exploited by adopting the ZnO@1-PyNH₂ core-shell structure. Unlike pristine 1-PyNH₂ molecules, the ZnO@1-PyNH₂ hybrid QDs formed energy proximity levels that enabled charge transfer. This result can be interpreted as an improvement in surface roughness. The uniform and homogeneous EML alleviates dark-spot degradation. Moreover, LEDs with the ITO/PEDOT:PSS/TFB/EML/TPBi/LiF/Al configuration were fabricated to evaluate the performance of two emissive materials, where pristine-1-PyNH₂ molecules and ZnO@1-PyNH₂ QDs were used as the EML materials to verify the improvement in electrical characteristics. The ZnO@1-PyNH₂ LEDs exhibited blue luminescence at 443 nm (FWHM = 49 nm), with a turn-on voltage of 4 V, maximum luminance of 1500 cd/m², maximum luminous efficiency of 0.66 cd/A, and power efficiency of 0.41 lm/W.

• Journal of Advanced Technology Convergence
• /
• v.2 no.4
• /
• pp.13-19
• /
• 2023

Following the signing of the Paris Agreement on Climate Change (UNFCCC, 2015), the world is expanding greenhouse gas reduction activities through comprehensive participation that includes not only developed countries but also developing countries. Major countries around the world are placing high expectations on the effectiveness of total carbon emissions regulation through the carbon emissions market. However, in order to obtain carbon credits, third-party verification is required based on quantitative carbon reduction data. Accordingly, in this paper, we developed an AIoT high-efficiency street light for carbon emissions and conducted a performance analysis study to measure the luminous efficiency of the lighting fixture. To obtain carbon emissions rights, we used high-efficiency LED PKG, developed our own high-voltage PFC, and developed high-efficiency lighting fixtures capable of communication. For communication, the 2.4GHz LoRa method was adopted between the lighting fixture and the gateway. Lens design was conducted through simulation of Korea Expressway Corporation's standard streetlight types A, B, and C. The performance of the streetlight was verified as being more efficient than other existing products through the measurement of luminous efficiency by an accredited rating agency, and it is expected that carbon emissions rights will be obtained by reducing electrical energy through this.

• International Journal of Highway Engineering
• /
• v.19 no.6
• /
• pp.165-173
• /
• 2017

PURPOSES : The current practice in car headlight visibility performance evaluation is based on the luminous intensity and illuminance of headlight. Such practice can be inappropriate from a visibility point of view where visibility indicates abilities to perceive an object ahead on the road. This study aimed at evaluating the appropriateness of current headlight evaluation method. METHODS : This study measured the luminance of object and road surface at unlit roadways. The variables were measured by vehicle type and by headlight lamp type. Based on the measurements, the distance where drivers can perceive an object ahead was calculated and then compared against such distance obtained by conventional visibility performance evaluation. RESULTS : The evaluation method based on illuminance of headlight is not appropriate when viewed from the visibility concept that is based on object-perceivable distance. Further, the results indicated a shorter object-perceiving distance even when road surface luminance is higher, thereby suggesting that illuminance of headlight and luminance of road surface are not the representative indices of nighttime visibility. CONCLUSIONS : Considering that this study utilized limited vehicle types and that road surface (background) luminance can vary depending on the characteristics of the given road surface, it would likely go too far to argue that this study's visibility performance evaluation results can get generalized to other conditions. Regardless, there is little doubt that the current performance evaluation criterion which is based on illuminance, is unreasonable. There should be future endeavors on the current subject which will need to explore study conditions further, under which more experiments should be conducted and effective methodologies developed for evaluating automotive headlight visibility performance. Needs are recognized particularly in the development of headlight visibility performance evaluation methodology which will take into account road surface (background) luminance and luminance contrast from various perspectives as the former indicates the driver's perception of the front road alignment and the latter being indicative of object perception performance.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.724-726
• /
• 2004

Highly efficient blue organic light-emitting devices (OLEDs) utilizing the idea of copper phthalocyanine (CuPc)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl,1,1'-biphenyl- 4,4'-diamine (NPB) composite hole transport layer (CPHTL) have been fabricated. The effect of inserting CPHTL upon the performance of blue OLEDs with 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) as the blue emitter has been investigated. Compared with the luminous efficiency of the standard blue device without CPHTL (1.33 cd/A), that of the device with 40:60 CuPc/NPB CPHTL has been increased by more than twice up to 2.96 cd/A with a Commission Internationale d'Eclairage (CIE) coordinates of(x = 0.15, y = 0.10) and a power efficiency of 1.46 lm/W (20 mA/$cm^2$) at 6.39 V. The increased device efficiency is attributed to an improved balance between hole and electron currents arriving at the recombination zone.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2004.08a
• /
• pp.272-276
• /
• 2004

Great strides in organic light emitting device (OLED) technology have resulted in a number of commercial products. To continue this growth into large area displays, for example televisions, an understanding of the mechanisms that drive the OLED device efficiency and lifetime performance is critical. In this work, we consider maximizing the efficiency lifetime product based on phosphorescent OLED ($PHOLED^{TM}$) technology. We report green PHOLEDs with luminous efficiency of 82 cd/A, 5.7 V and 10,000 hours lifetime at 1,000 cd/$m^2$,red PHOLEDs with CIE of (0.67,0.33), 11 cd/A and 35,000 hours lifetime at 500 cd/$m^2$ and recent progress in blue demonstrating efficiencies of 18 cd/A at 200 cd/$m^2$.