見張りの妨げとなるサングリッターの影響とサングラスの評価

Abstract

The sun glitter caused by the reflection of the direct solar radiation. This report is the experimental study of the sun glitter influence on the visual performance, and of the most effective sunglasses which can reduce the sun glitter influence for the watch-keeping seafarers on the navigation bridge. The instruments are two types of device, one is the vision tester called OPTEC-2000 which can measure the contrast sensitivity ; the other one is the flicker tester. The results obtained from this experiment on board are as follows ; 1. The mean level of the luminance of the sea surface below the horizon at approximately one degree is 2×10^5cd/m^2. The maximum level is 1×10^6cd/m^2. This sun glitter influence occurs after sunrise and again before sunset. 2. The sun glitter is a disability glare which lowers the visual performance greatly. 3. Evaluation of sunglasses. (1) The use of sunglasses has the effect of counteracting the reduction of visual perform ance caused by the sun glitter. (2) The most effective sunglasses to counteract the sun glitter influence The transmitted color is the green group which has the characteristics of absorbing the wave length of the visible range, of course including the ultraviolet radiation. There is a tendency that the 20% transmittance of the green group sunglasses has a little influence on the visual performance. (3) There are some cases where polarized sunglasses are used to look through the windshield of the navigation bridge. This causes stripes to appear on the visual field. 4. For the watch-keeping seafarers on the navigation bridge, it is important to use the sunglasses mentioned above in order to combat the effects of the reduction of visual performance caused by the sun glitter influence.