The Study Of Comfort In Office Lighting With LEDs

With the advantages such as energy-saving, environmental protection and long lifetime, LED light source has become the representative of the fourth generation light sources and the most preferred light source for green lighting in 21st century. LED light source is expected to gradually replace traditional light sources in ordinary indoor lighting, hence, investigation on the comfort in LED lighting is of great importance for future lighting designs. In this thesis, the comfort in office lighting with LEDs was mainly studied.The development history of light sources, the basic factors for indoor lighting quality and the lighting application of LEDs were introduced firstly, and the significance of researches on the comfort in LED lighting was emphasized. The research situation and research methods for comfort in lighting were then introduced, including subjective assessment and objective measurement based on the variation of physiological parameters which were applied in this thesis.The subjective assessment was used to investigate the influence of luminaire spacing on visual comfort and the effect of two working modes (computer work and reading on desk) on glare perception in office environment. The results show that in office lighting with equal luminaire spacing, the impact of two different luminaire spacings (120cm and 180cm) on visual comfort and subjective space brightness was not significant. Therefore, a luminaire spacing of 180cm can be used for the purpose of energy-saving. The research on different working modes in office environment showed an increase in perceived glare with increasing luminaire luminance, and perceived overhead glare from one single glare source increased as it came closer to the viewer’s horizontal line of sight. The results showed an significant effect of different working modes on glare perception in office lighting, the perceived glare in computer work was more serious than that in the mode of reading on desk.The uniformity of luminance distribution of lighting conditions was analyzed with the Fourier transform of luminance matrix. Experimental results showed that the perceived glare changed with the value of vertical illuminance at eye position according to the same tendency for different types of luminaire, and there was a correlation between glare and the uniformity of luminance distribution. Therefore, a common glare calculation model based on the value of vertical illuminance at eye position and the uniformity of luminance distribution was established.Finally, physiological parameters measurement and analysis were used for the exploratory research on comfort in AC-LED lighting. The experimental results showed that when a modulation depth at the acceptable threshold (75%) of stroboscopic effect was used, there was no significant difference in stroboscopic effect and comfort between AC-LED lighting and fluorescent lighting. While AC-LED lighting with 100% modulation depth showed visible stroboscopic effect and generated more human discomfort. Moreover, analysis on the physiological parameters showed that as the degree of fatigue increased and human comfort decreased, the heart rate would decrease.