漁網の水中視程に関する研究-I : 水の濁りと網系の視程について

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Visual range of net twines with different colors and diameters (Table 1) was observed succesively in an experimental tank (Fig. 1) containing water of serially different turbidity (Fig. 2). Variations of visual range with the wave length of incident light was also observed using a series of color filters (Table 2 and Fig. 3). Visibility or visual range γ of net twine in water of turbidity k seen from the light source of parallel illumination is expressed by the following equation; ε=e-2kr(8R/f180-1), where ε is the contrast threshold of observer, R is the luminous albedo of the net twine and f180 is the mean relative backward scattering function of surrounding water. The value of ε of an observer is generally a function of the brightness of background and the visual angle θ of target. In this experiment the value of ε was calculated by observing long and narrow strips of grayish paper of different width with known albedo, backgrounded by a constant brightness, and the following experimental formula was obtained (Fig. 4 and Fig. 5); ε=ε0/1-e-θθ where ε0 and α are parametric constants depending probably on the background brightness and the shape of target, respectively. The backward scattering is generally very difficult to obtain, therefore the values of ε/e-2kr=8R/f180-1≅B were calculated to test their constancy through a series of experiments with a fixed twine (sample No. 1) and any one fixed color filter, the results being shown in Table 4. The variation of this value with the turbidity of water is not negligibly small except in the case of green light.
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漁網の水中視程に関する研究-I : 水の濁りと網系の視程について

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