An experiment was carried out to examine the method of adjustment when determining user preferences for the colour appearance of ambient lighting. A booth was lit using luminaires containing an array of white and coloured light emitting diodes (LEDs), allowing continuous variation of correlated colour temperature (CCT) between 2736 and 4014 K. It was predicted that the preferred CCT would be influenced by the available stimulus range, the anchor (initial setting before adjustment), adaptation time before onset of adjustment action and type of control dial. Preference was estimated for three different CCT stimulus ranges within the available range. All three ranges led to significantly different results for preferred CCT: 3288, 3490 and 3671 K. The experimental results confirmed that stimulus range, anchor and adaptation time have significant effect on the preferred CCT determined using the adjustment task, and thus, the importance of considering and reporting this information in studies that employ the method of adjustment.
Fluorescent Light Energy (FLE) is a unique form of photobiomodulation that stimulates healing, reduces inflammation, and alleviates pain. The system works by exciting a chromophore in a topical substrate, which emits FLE with a broad spectral range (~400-700 nm) that is delivered to the target tissue below. Results from in vivo and in vitro studies have shown FLE modulates inflammation via down-regulation of pro-inflammatory cytokines such as IL-6 and TNF-α, and stimulates mitochondria biogenesis 1. A recent study showed FLE-stimulated cells responded more potently compared to cells treated with light from an LED light source ("Mimicking Lamp") designed to generate the same emission spectra and power intensity profile as FLE 2. FLE-treated human dermal fibroblasts (HDF) experienced up-regulated collagen production, while a minor and nonsignificant effect was observed for the Mimicking Lamp-treated HDFs. These results suggest that photons generated by FLE either penetrate tissue differently or are absorbed differently compared to photons from a LED light source. Photonic properties of FLE that could impact tissue penetration or absorption may include polarity or coherency, leading to different cellular responses. To investigate if light polarity may influence cellular responses to FLE stimulation, the present study applied linear and circular-polarizing filters to investigate the influence of FLE's polarity on immune parameters. The data suggest that FLE polarity contributes to its impact on biological systems. Furthermore, the immunemodulatory impact of FLE was investgated in a pilot study on a human ex vivo skin model suggesting that central myeloid immune surface markes are modulated by FLE.
We report observations of saturation effects in a Ce:LuAG and Eu-doped nitride ceramic phosphor for conversion of blue laser light for white light generation. The luminous flux from the phosphors material increases linearly with the input power until saturation effects limit the conversion. It is shown that the temperature of the phosphor layer influences the saturation power level and the conversion efficiency. It is also shown that the correlated color temperature (CCT), phosphor conversion efficiency and color rendering index (CRI) are dependent both on the incident power and spot size diameter of the illumination. A phosphor conversion efficiency up to 140.8 lm/W with CRI of 89.4 was achieved. The saturation in a ceramic phosphor, when illuminated by high intensity laser diodes, is estimated to play the main role in limiting the available luminance from laser-based lighting systems.
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