| 摘要 |
PURPOSE:To match horizontal section oblique incident light characteristics of a photodetection part with (1+costheta)/2 with accuracy where there is no practical problem by setting the ratio of the size of a light shield hood to the size of a diffusion plate arranged in front of the light shield hood to >=10. CONSTITUTION:The shape and position relation are so determined that the outputs of photoelectric converting elements 4 and 5 are shown by relation (1+costheta)/2 to the incidence angle of light when the light is made incident on the diffusion plates 1 and 2 at 0-180 deg. horizontal angles and relation costheta when the light is incident at 0-90 deg. and 270-0 deg. vertical angles. Further, the light shield hood 3 which cuts off light in the direction where it is measured by the diffusion plate 1 is arranged in front of the diffusion plate 2 and a space is left by the size r1 of the diffusion plate 2 so that light at 90 and 270 deg. to the diffusion plate 2 is not cut off. Here, when the size of the hood 3 is denoted as r2 and r2/r1=10, the value of each measurement error resulting from the space is about 4%. For the purpose, the ratio r2/r1 is set to >=10 and then the photodetection part takes a measurement without a permissible error range.
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