- 一般社団法人 照明学会
- 照明学会雑誌 (ISSN:00192341)
- vol.47, no.6, pp.234-239, 1963 (Released:2011-07-19)
For the measurement of the extinction coefficient of light through the atmosphere, the layout of instruments on a large scale is usually needed. Methods to estimate the extinction coefficient σ or σλ by measurements with simple portable instruments and computations are studied.In the first method, targets shown in Fig. 3 are used and σ is estimated from the reduction of contrast and the known values of contrast threshold.In the second method a is obtained from the visual range of large dark objects.In the third method σ is estimated from the change of apparent luminance of natural objects with distance. The spectral extinction coefficient σλ is computed by equations (11) from the change of apparent colors, where σλ is assumed to be σo (λo/λ) n. Thereby electronic computation is applied and the solution is obtained graphically.Though high accuracy is not expected from these methods, a large number of data are easily obtained because of experimental simplicity and they can be applied to the discussion of visibility for the traffic safety.