コントラストの識閾計算について (人間の目による網糸の水中程の研究-2,3-〔英文〕)

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The visibility of an object depends upon the brightness of the water space in the solid angle which the object subtends to the eye and the brightness of the background. In this paper, the results of measurements were analysed by using a formula which was derived by modifying the theoretical equation presented by Koschmieder and Middleton for visibility in the atmosphere so that it was applicable to the experimental conditions of the present studies. The equation for the visibility is as follows, ε=|R•H2•Q•h/KA-1b•E(1-e-kr)•π2•∫r0p/(h2+p2)2•exp[-K(√h2+p2+r)]dp+R.e-kr(1-e-kr)+e-kr-e-kL/1-e-kL| In transparent twines, the equation requires some correction because we have to con-sider transparent radiance at the observer's eye. In the estimation, the thresholds of brightness-contrast increase almost rectilinearlly with the decrease of the visual angle in the region of small visual angles and these relationships agree with the experimental results of Blackwell for the atmosphere. We have examined the relationship between the luminous reflectance of the object and its visual range. It is shown that the visual ranges decrease remarkbly when the luminous reflectance value is taken as 10% but increase rapidly with further decrease of it. In the case of transparent twines, we can not observe the objects as a silhoutte under 3%.
日本水産學會の論文