• 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.

• Molecules and Cells
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• v.23 no.2
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• pp.154-160
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• 2007

An Arabidopsis hy4 mutant that is specifically impaired in its ability to undergo blue light dependent photomorphogenesis was used to identify cryptochrome 1 signaling-related components. Proteomic analysis revealed about 205 differentially expressed protein spots in the blue light-irradiated hy4 mutant compared to the wild-type. The proteins corresponding to 28 up-regulated and 33 down-regulated spots were identified. Obvious morphological changes in the hy4 mutant were closely related to the expression of various transcription factors. Our findings suggest that blue light signals may be involved in many cellular processes including disease resistance and stress responses.

• 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.

• 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.

• 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.

• Journal of Plant Biology
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• v.38 no.1
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• pp.1-10
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• 1995

Photoinhibition and its recovery of spectrally adapted Anacystis nidulans were studied. Phycocyanin and Chl content and phycocyanin/Chl ratio were increased in cells grown under blue-green light compared with those grown in white light. Photosynthetic activities of white light and blue-green light grown cells were reduced by 50% after 15 min and 10 min of photoinhibitory light treatment (1.2 mmol·m-2s-1), respectively, largely due to the decline of PSII activities. However, their activities were recovered fully after 30 min incubation under weak light. Treatment of rifampicin and chloramphenicol magnified the photoinhibitory effects and suppressed the recovery with disappearance of susceptibility to photoinhibition and delayed the recovery process, indicating no significant differences in phosphorylation, dephosphorylation and protease activity between two cells. Therefore, it is suggested that the increased sensitivity of blue-green adapted cells might be attributed to the decline of protein synthesis, and phosphorylation-dephosphorylation of protein and protease activity might be involved in the recovery process.

• Korean Journal of Environment and Ecology
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• v.31 no.1
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• pp.88-92
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• 2017

This study investigated the growth and maturation of free conchocelis of Pyropia yezoensis under monochromatic light of blue light(480 nm), green light(550 nm), yellow light(600 nm) and red light(730 nm) which measured the colony diameter, content of chlorophyll a and conchosporangium formation. In the result, the most of colony diameter and chlorophyll a showed under the blue light, $2,472.6{\pm}27.0{\mu}m$ and $1.55{\pm}0.03mg\;g.dw^{-1}$. Also, the chlrophyll a content of conchocelis was under the blue light. Therefore, the blue light might be favorable for the growth and maturation of conchocelis of P. yezoensis. This study will lead development of indoor culture technologies.

• Journal of Ecology and Environment
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• v.42 no.4
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• pp.174-182
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• 2018

Background: In this study, we observed their growth and physiological responses using a variety of duty ratio under the mixed light using red, blue, and white lights. The red+blue mixed light was treated with 95%, 90%, 85%, 80%, and 75% duty ratios and red+blue+white mixed light with 85% and 70% duty ratios. We examined the width and length of leaves, total number of leaves, and number of shoots to examine their growth responses. The physiological responses were studied by measuring their photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency, chlorophyll content, and fluorescence ($F_o$, $F_m$, and $F_v/F_m$). Results: We found that lower duty ratio caused the length and width of the leaves to grow longer under red+blue mixed light but that it did not cause any difference in the red+blue+white mixed light condition. In addition, there was no difference in the number of leaves and shoots among all treatments. In the red+blue mixed light condition, the photosynthetic rate was no difference, but both transpiration rate and stomatal conductance were the highest at 95% duty ratio than in other ratios. Water use efficiency pattern was similar to that of photosynthetic rate; water use efficiency was no difference. Chlorophyll content was the highest at 95% duty ratios, and it was the least at 90%, 85%, and 75% duty ratio. $F_o$ and $F_m$ values were relatively high at 85% and 80% duty ratio and low at 90% duty ratio while $F_v/F_m$ showed no difference. Conclusions: Under the red+blue+white mixed light, all physiological items showed no difference between 70 and 85% treatments. But, photosynthetic rate, water use efficiency, chlorophyll content, and $F_v/F_m$ were relatively greater in the red+blue+white mixed light than in the red+blue mixed light. Therefore, red+blue+white mixed light treated with 70% duty ratio could lessen the environmental stress and save more power when cultivating Silene capitata in a plant factory.

• Horticultural Science & Technology
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• v.30 no.1
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• pp.6-12
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• 2012

Early growth, pigmentation, protein content, and phenylalanine ammonia-lyase (PAL) activity of red curly lettuces (Lactuca sativa L.) grown under different lighting conditions were investigated. Fluorescent lamps (control), blue, red, and blue plus red light-emitting diodes (LEDs) were used as light sources for 10 days. An equal proportion (1:1) of blue and red LEDs was used in the mixed radiation condition. Compared with the control, monochromic red or blue lighting increased fresh and dry weights of 'Ttuksum' and 'Jaju' lettuces. Anthocyanin synthesis was also significantly promoted by the mixed radiation of blue and red LEDs. The mixed radiation also increased the protein content and PAL enzyme activity of 'Ttuksum' leaves by about 200% compared to other treatments. Anthocyanin content was the highest in lettuces subjected to the mixture radiation of blue and red light treatment, while anthocyanin synthesis was inhibited by monochromic red light. The results of the present study indicate that growth and pigment synthesis in lettuces are significantly enhanced by exposure to mixed radiation from blue and red LEDs.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.12a
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• pp.62-62
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• 2020

Ginseng is a shade-plant cultivated using shading facilities. However, at too low light levels, root growth is poor, and at high light levels, the destruction of chlorophyll reduces the photosynthesis efficiency due to leaf burn and early fall leaves. The ginseng has a lightsaturation point of 12,000~15,000 lux when grown at 15 to 20℃ and 9,500 lux at 25℃. This study was conducted to select the optimal light intensity of 3-year-old ginseng grown in blue-white film plastic house. The seeds were planted in the blue-white film plastic house with different light receiving rate (March 17, 2020). Between April and September, the average air temperature in the house was 20.4-20.7℃. Average soil temperature was 18.3℃-18.5℃. The chemical properties of the test soil was as follows. The pH level was 7.0-7.4, EC was 0.5-0.6 dS/m, OM was at the levels of 33.6-37.7 g/kg, P₂O₅ was 513.0-590.8 mg/kg, slightly higher than the allowable 400 mg/kg. The amount of light intensity, illuminance, and solar radiation in the blue-white film house was increased as the light-receiving rate increased and the amount of light intensity was found to be 9-14% compared to the open field, 8-13% illuminance and 9-14% solar irradiation respectively. The photosynthesis rate was the lowest at 3.1 µmolCO²/m²/s in the 9% light blue-white plastic house and 4.2 and 4.0 µmolCO²/m²/s in the 12% and 14% light blue-white plastic house, respectively. These results generally indicate that the photosynthesis of plants increases with the amount of light, but the ginseng has a lower light saturation point at high temperatures, and the higher the amount of light, the lower the photosynthetic efficiency. The SPAD (chlorophyll content) value decreased as the increase of light-receiving rate, and was the highest at 32.7 in 9% light blue-white plastic house. Ginseng germination started on April 11 and took 13-15 days to germinate. The overall germination rate was 82.9-85.8%. The plant height and length of stem were long in the 9% light-receiving plastic house. The diameter of stem was thick in the 12-14% light-receiving plastic house. In the 12% and 14% light-receiving plastic house, the length and diameter of taproot was long and thick, so the fresh weight of root per plant was 20 g or more, which was heavier than 16.9 g of the 9% light-receiving plastic house. The disease incidence (Alternaria blight, Gray mold and Damping-off etc.) rate were 0.9-2.7%. The incidence of Sclerotinia rot disease was 7.5-8.4%, and root rot was 0-20.0%. The incidence ratio of rusty root ginseng was 34.4-38.7% level, which was an increase from the previous year's 15% level.