• Korean Journal of Fisheries and Aquatic Sciences
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• v.39 no.6
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• pp.480-486
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• 2006

The radiation characteristics of a high-luminance light-emitting diode (LED) light source were studied to evaluate its potential as an energy-saving light source for fishing lamps. The angle of the LED light source with 50% illuminance was $8-15^{\circ}$, and it had strong directional characteristics. The wavelengths at which the radiance and irradiance were maxima were 709, 613, 473, 501, 525, and 465 nm for red, orange, blue, peacock blue, green, and white light, respectively. The underwater transmission characteristics of the LED light source were superior in the order blue, white, peacock blue, and green in optical water type I: blue, peacock blue, white, and green in optical water type II; and blue, peacock blue, green, and white in optical water type III. Setting the underwater transmission characteristics of the LED light source in optical water type I at 100%, the transmission of water types II and III decreased to 67 and 17%, respectively. Based on the underwater transmission characteristics calculated in optical water types I-III, the blue and peacock blue LED light sources can be used as an energy-saving light source for fishing lamps.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.3
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• pp.293-300
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• 2015

Purpose: To evaluate blue light hazards of LED lightings in an optical store with blue light radiance used as the quantitative indicators of photobiological hazard. Methods: The spectral radiance of each LED lightings was measured, and blue-light radiance and the corresponding maximum exposure time were calculated. Then each LED lighting was classified according to the risk group from IEC 62471 standard. Results: The yellow LED lightings used in showcases and white LED lightings used on ceilings and logo were classified into risk group RG0. But the white LED lightings used on showcases were classified into risk group RG1. The blue light radiances of white LED lightings used in showcases are dozens of times larger than that of fluorescent lamp. Conclusions: Using the value of the blue light radiance could quantitatively express the blue light hazard to various lightings. It was confirmed that white LED lightings for the showcases had high blue light hazards because of their high luminance and color temperature. Therefore, when replacing lightings in optical shop it is necessary to select the appropriate brightness and color temperature for eye health in the long term.

• Journal of Bio-Environment Control
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• v.31 no.1
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• pp.60-66
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• 2022

This study was conducted to investigate growth characteristics of paprika seedlings according to various qualities of LED light (red : blue = 10 : 0, red : blue = 8 : 2, red : blue = 2 : 8, white). Plant height and stem were significantly longer or thicker as red light ratio increased. Leaf area of paprika seedlings with red light was larger or no significant differences in a mixed light of red and blue. Dry weight of seedling was in the same with the result of leaf area. Seedlings with White light was significantly less than others in all characteristics. As red light ratio was increased, relative growth rate increased. As blue light ratio was increased, the net assimilation amount increased. Considering plant height, leaf area and production ability of dry matter per unit leaf area, the using mixed red and blue lights was suitable, especially at a mixed red : blue = 8 : 2.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7256-7261
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• 2015

This paper devised a plant growing system As LED light source, three monochromatic lights (red, blue, white) and three mixed lights (red1+blue1, red2+blue1, red1+blue2) were made. According to the optical properties of those LED light sources and change in the amount of light, this author analyzed the characteristics of luminance and PPFD and also plant growth. According to the light efficiency of those LED light sources, it was high in white light as 125 lm/W and was low in red1+blue2 light as 9.9 lm/W. This result shows that monochromatic light has higher light efficiency than mixed light. The PPFD ($25{\mu}mol$, $50{\mu}mol$, $100{\mu}mol$) luminance in different wavelengths of LEDs was high in white LEDs and was low in blue LEDs. therefore, it is possible to devise an efficient LED lighting system appropriate for growing plants by variety monochromatic lights and mixed light wave length combination of LED light source.

• Korean Journal of Ecology and Environment
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• v.52 no.2
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• pp.171-177
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• 2019

Smart farm is a breakthrough technology that can maximize crop productivity and economy through efficient utilization of space regardless of external environmental factors. This study was conducted to investigate the optimal growth and physiological conditions of Chinese matrimony vine (Lycium chinense) with LED light sources in a smart farm. The light source was composed of red+blue and red+blue+white mixed light using a LED system. In the red+blue mixed light, red and blue colored LEDs were mixed at ratios of 1:1, 2:1, 5:1, and 10:1, with duty ratios varied to 100%, 99%, and 97%. The experimental results showed that the photosynthetic rate according to the types of light sources did not show statistically significant differences. Meanwhile, the photosynthetic rate according to the mixed ratio of the red and the blue light was highest with the red light and blue LED ratio of 1:1 while the water use efficiency was highest with the red and blue LED ratio of 2:1. The photosynthetic rate according to duty ratio was highest with the duty ratio of 99% under the mixed light condition of red+blue+white whereas the water use efficiency was highest with the duty ratio of 97% under the mixed light of red+blue LED. The results indicate that the light source and light quality for the optimal growth of Lycium chinense in the smart farm using the LED system are the mixed light of red+blue (1:1) and the duty ratio of 97%.

• Journal of the Optical Society of Korea
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• v.17 no.1
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• pp.22-26
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• 2013

The author analyzes the luminous efficiency of the phosphor-conversion white light-emitting diode (LED) that consists of a blue LED chip and a yellow phosphor. A theoretical model is derived to find the relation between luminous efficiency (LE) of a white LED, wall-plug efficiency (WPE) of a blue LED chip, and the phosphor absorption ratio of blue light. The presented model enables to obtain the theoretical limit of LE and the lower bound of WPE. When the efficiency model is applied to the measured results of a phosphor-conversion white LED, the limit theoretical value of LE is obtained to be 261 lm/W. In addition, for LE of 88 lm/W at 350 mA, the lower bound of WPE in the blue LED chip is found to be ~34%. The phosphor absorption ratio of blue light was found to have an important role in optimizing the luminous efficiency and colorimetric properties of phosphor-conversion white LEDs.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.6
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• pp.511-517
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• 2008

The radiation characteristics and economic efficiency of high - luminance light - emitting diodes (LEDs), a metal halide lamp, and a halogen lamp were studied to evaluate their potential as an energy-saving light source for fishing lamps. The wavelengths at which irradiance was maximum were 709, 613, 473, 501, 525, 465, 578, and 973 nm for red, orange, blue, peacock blue, green, and white LEDs, the metal halide lamp, and the halogen lamp, respectively. If the irradiance characteristics at 300-1,100 nm wavelengths are set as 100%, the irradiance rates at 381-780 nm were 99-78%, 82%, and 24% for the LEDs, metal halide lamp, and halogen lamp, respectively. The economic efficiency was superior in the order metal halide lamp, halogen lamp, peacock blue LED, and blue LED at 381-780 nm and metal halide lamp, peacock blue LED, blue LED, and halogen lamp at 480-520 nm. Based on the radiation characteristics and economic efficiency evaluated at 480-520 nm, the blue and peacock blue LED light sources can be used as energy-saving light sources for fishing lamps.

• Journal of Biosystems Engineering
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• v.38 no.4
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• pp.279-286
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• 2013

Purpose: This study was conducted to analyze the utilization efficiencies of electric energy and photosynthetically active radiation of lettuce grown under red LED, blue LED and fluorescent lamps with different photoperiods. Methods: Red LED with peak wavelength of 660 nm and blue LED with peak wavelength of 450 nm were used to analyze the effect of three levels of photoperiod (12/12 h, 16/8 h, 20/4 h) of LED illumination on light utilization efficiency of lettuce grown hydroponically in a closed plant production system (CPPS). Cool-white fluorescent lamps (FL) were used as the control. Photosynthetic photon flux, air temperature and relative humidity in CPPS were maintained at 230 ${\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, $22/18^{\circ}C$ (light/darkness), and 70%, respectively. Electric conductivity and pH were controlled at 1.5-1.8 $dS{\cdot}m^{-1}$ and 5.5-6.0, respectively. The light utilization efficiency based on the chemical energy converted by photosynthesis, the accumulated electric energy consumed by artificial lighting sources, and the accumulated photosynthetically active radiation illuminated from artificial lighting sources were calculated. Results: As compared to the control, we found that the accumulated electric energy consumption decreased by 75.6% for red LED and by 70.7% for blue LED. The accumulated photosynthetically active radiation illuminated from red LED and blue LED decreased by 43.8% and 33.5%, respectively, compared with the control. The electric energy utilization efficiency (EEUE) of lettuce at growth stage 2 was 1.29-2.06% for red LED, 0.76-1.53% for blue LED, and 0.25-0.41% for FL. The photosynthetically active radiation utilization efficiency (PARUE) of lettuce was 6.25-9.95% for red LED, 3.75-7.49% for blue LED, and 2.77-4.62% for FL. EEUE and PARUE significantly increased with the increasing light period. Conclusions: From these results, illumination time of 16-20 h in a day was proposed to improve the light utilization efficiency of lettuce grown in a plant factory.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.3
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• pp.59-68
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• 2023

Currently, yellow phosphor of Y3Al5O12:Ce3+ (YAG:Ce) fluorescent material is applied to a 450~480nm blue LED light source to implement a white LED device and it has a simple structure, can obtain sufficient luminance, and is economical. However, in this method, in terms of spectrum analysis, it is difficult to mass-produce white LEDs having the same color coordinates due to color separation cause by the wide wavelength gap between blue and yellow band. There is a disadvantage that it is difficult to control optical properties such as color stability and color rendering. In addition, this method does not emit purple light in the range of 380 to 420nm, so it is white without purple color that can not implement the spectrum of the entire visible light spectrum as like sunlight. Because of this, it is difficult to implement a color rendering index(CRI) of 90 or higher, and natural light characteristics such as sunlight can not be expected. For this, need for a method of implementing sunlight with one LED by using a method of combining phosphors with one light source, rather than a method of combining red, blue, and yellow LEDs. Using this method, the characteristics of an artificial sunlight LED device with a spectrum similar to that of sunlight were demonstrated by implementing LED devices of various color temperatures with high color rendering by injecting phosphors into a 405nm deep blue LED light source. In order to find the spectrum closest to sunlight, different combinations of phosphors were repeatedly fabricated and tested. In addition, reliability and mass productivity were verified through temperature and humidity tests and ink penetration tests.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.3
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• pp.266-274
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• 2023

Recently, sterilization technology has received increasing interest due to the COVID-19 pandemic and required safety precautions. Particularly, sterilization devices using near ultraviolet (UV) with a 405 nm wavelength are also drawing attention. It has a UV-C wavelength and other sterilization effects. Its blue-colored light on the boundary between UV and visible light is used as a light-emitting diode (LED) lamp for 405 nm sterilization, owing to its longer wavelengths than UV rays. However, the 405 nm wavelength contains blue light that can damage the eyes and skin during prolonged exposures and affect the emotional and biological parts of the body. Currently, 405 nm sterilization LED light registers are circulating in the market. However, they have not undergone safety tests for blue-light hazards. Thus, with the active distribution of sterilization LED lights, solid safety standards and management systems are essential to protect users from blue-light hazards. Accordingly, in this study, we conducted spectral radiance and spectral radiative luminance tests on 405 nm sterilization LED registers available in the market by the measurement criteria of IEC 62471. Safety standards must be established to secure users' safety against blue light hazards at a time when 405nm sterilization LED lights are actively distributed due to COVID-19.