Luminance-based visibility evaluation methods can enhance lighting design flexibility in near future, in which case edge detection technologies will be essential. We developed an edge detection method by including a normalization algorithm based on neurophysiology and validated it by examining the relationship to subjective evaluation in tunnel spaces. The result showed that the algorithm in this research could estimate the visibility with sufficient accuracy. In the future, this algorithm will need to be combined with the optical mechanism in visual systems and compared with other algorithms with different parameters settings to further validate this method.

Road-projection technology has been developed to improve traffic safety, in which symbols or patterns are projected onto the road surface from a vehicle. The response times of cyclists when a vehicle direction indicator flash with and without road-projection were obtained to verify alerting effects of the road-projection lamp linked to the direction-indicator of the vehicle. When cyclists could not see the direction-indicator lamp flashing on the vehicle or when they were moving by a bicycle, the response times with road-projection were shorter than those without it. Favorable responses were received from participants through the questionnaire used in this study regarding the road projection of the direction-indicator. Even when cyclists were operating smartphones, the response times with road-projection were shorter than without it. However, this suggested that delays caused by operating smartphones were longer than the time saved by road-projection.

A viral fluid containing coronavirus OC43 was smeared onto plastic surfaces and irradiated with light at wavelengths of 222, 254, and 275 nm emitted by an excimer lamp, an ultraviolet lamp, and a deep ultraviolet LED, respectively. After irradiation at varying durations, the virus on the plastic surface was collected and the viral activity was measured to compare the viral inactivation capabilities of the three wavelengths. We found that the 275-nm light from the deep ultraviolet LED exhibited an inactivating effect greater than or equal to the 254-nm light from the UV lamp that is used as a sterilizing device in general applications. The results demonstrated the potential of deep ultraviolet LED irradiation for general viral infection control and in the ongoing fight against the novel coronavirus, SARS-CoV-2.

The overall lightness of the whole surface of a fabric under non-uniform and uniform lighting conditions was investigated. In the experiment, the perceived lightness of the bright, dark, and whole area of pieces of glossy and matte fabric placed on a pseudo-sine-wave board under different combinations of directional and diffused lights was measured by matching the lightness to a reference grayscale placed in the matching box with a diffused light. The perceived lightness of the bright and dark areas could be expressed with a linear function of the logarithmic luminance of each area for both the glossy and matte fabrics. The perceived overall lightness under the non-uniform lighting conditions with directional light was close to that of the dark area with no significant contribution of the lightness of the bright area. This is consistent with the previous study which showed the elimination of highlights in the lightness judgment. However, contribution of the bright area was not nothing because it raised the perceived lightness value about 1.2 times higher than that of the dark area. On the other hand, the overall lightness under the uniform lighting condition with diffused light only was estimated by the weighing sum of the perceived lightness of bright and dark areas. Further investigation into the effects of spotlight size, its luminance, luminance contrast between the bright and dark areas, and the glossiness of fabric is necessary.