航行安全上からみた航海者のための視覚伝達に関する研究-I : 各種灯火の実状調査に基づくシミュレータの利用

抄録

For the navigators during coastal navigation at night, lamplights such as the navigational aids and the ship light of other ships should have a good visual transmission from the view point of navigation safety. There are many cases, however, in which the visual cognition of these lamplights has become difficult due to the intensity of light, the colour and shape of these lamplights, or miscellaneous lights of the background. For such reason, the object of this study is to intend to grasp quantitatively by making analyses of the factors and by means of an entirely new method. From the result of investigations of visual degree of lamplights at sea, the followings have been confirmed. (1) In case the objective of visual cognition is a point light source, from the visual feeling, the relation to the background is liable to be seen as a quadratic dimension, and on the other hand, in case the objective of visual cognition is a face light source, the relation to the background is apt to be seen as a cubic dimension. (2) The intensity of light and the colour of the background of the objective of visual cognition have an effect on the visual transmission. It can be said from the foregoing two items that the intensity of light, the colour and shape are the fundamental factors. As for the measuring of the background light, as a result of employment of a wide-angle brightness meter of 20°visual field, it was found that the medium and small sized cities and towns at night have brightness of about 10^<-1>(cd/m^2) at maximum. Furthermore, as for the quantitative study of various factors, it is necessary to have a device capable of changing the character of lamplights freely. Therefore, an indoor experiment was conducted with the utilization of a fog box 5m in length, 1m in height and 2m in breadth. For the transmission of light, an optical fiber was used. One end of the optical fiber was arranged to the light source, designing to enable the light from various light sources to be radiated. And thus, when observed from the other end in the fog box, it has become clear that the adequate brightness of the objective of observation is dependent upon the background brightness, having correlations. From the foregoing results, this new method of experiment is considered to be appropriate, and thereby a direction for the future studies has been secured. This study was conducted in parallel with the investigation and study concerning the lighting of bridges and the navigational aids among those undertakings carried out by the Japan Association for Preventing Marine Accidents for navigation safety entrusted by the Honshu-Shikoku Bridge Construction Public Corporation.