| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a device for determining the presence or absence of direct light easy for maintenance management and capable of accurately determining the presence or absence of direct light.SOLUTION: The device for determining the presence or absence of direct light includes: first determination means 5 for determining the presence or absence of the current direct light and second determination means 5 for determining that it is a half clear sky day when a brightness fluctuation other than the position of the sun is great when determined as absence of current direct light by the first determination means 5.</p> |
