In late years fluctuation lighting systems have been installed for the purpose of energy saving in the office. This is the light control system using motion sensor, which automatically conducts the light off from the absent seat. These systems save time to adjust lighting and can save electricity effectively. However, the physiological effects resulting from fluctuation lighting to the area workers are highly uncertain. The rapid change of illuminance might make office workers feel unpleasant. It is also predicted that the slow attenuate of illuminance may be effective as which the workers are not conscious of the change. On the psychological evaluations of slow attenuate lighting, Kokubu et al. (2015) found that 0.7 illuminance ratio between pre and post attenuation of illuminance does not cause subjective awareness.
We focused on physiological effects in this study, and tested it for the purpose of examining a change of the prefrontal cerebral blood flow of the subjects by the slow attenuation of illuminance of lighting, using NIRS and the same experimental designs of Kokubu et al. (2015). By experiment 1, we examined prefrontal cerebral blood under the slow attenuation illuminance of lighting using daylight fluorescent light as common office lighting. In experiment 2, we used light bulb color fluorescent light instead of daylight color, and conducted the same experimental design of the experiment 1. By experiment 3, we examined rapid attenuation of illuminance of lighting conditions using daylight fluorescent light. Details of these experiments are given in Chapter 2.
As the result, we found that the pre-attenuate illuminance conditions and illuminance attenuation itself affect changes of cerebral blood flow. In the conditions of attenuate rate 12.5lx/s and 75x/s, cerebral blood flow increased on 1000lx in comparison to 500lx under illuminance ratio 0.7 conditions. However, the subjects did not feel darkness and awareness about decreasing illuminance under 1000lx pre-attenuate illuminance condition. On the other hand, cerebral blood flow increased smaller on the conditions of rapid attenuate rate 300lx/s or more than on the conditions of slow attenuation lighting. Subjects recognized clear awareness for the illuminance change on the rapid attenuate illuminance conditions, and evaluated to be hard to concentrate on writing and calculation tasks. Thus, it was found that the change of the cerebral blood flow in the prefrontal area and the amount of the stress caused by illuminance change did not correlate with each other. These results may suggest that increase of prefrontal cerebral blood flow on the slow attenuation of illuminance conditions cause concentration of the tasks, instead of feeling stress. Results of three experiments are shown in chapter 3 to 6. Discussion of results of three experiments is given in Chapter 7.