| 摘要 |
PROBLEM TO BE SOLVED: To enable accurate determination of air filter clogging.SOLUTION: When detected illuminance is below theoretical illuminance P, it is estimated that illuminance of a light source part 11 has fallen with a temperature increase of an ambient temperature Ta. In this case, deviation from the theoretical illuminance P is read (step S9), and then, determination is made whether the read deviation amount is 80% or more with respect to the theoretical illuminance P (step S10). When the determination is YES, and the deviation amount is 80% or more, the actual illuminance of the light source part 11 has fallen greatly with respect to the theoretical illuminance P. Thus, it is estimated that in the light source part 11, the illuminance has fallen greatly due to a thermal influence generated by increase in an internal temperature. Further, it can be determined that the thermal influence generated by the increase in the internal temperature has been caused by clogging in an air filter 5. Thus, in a display part 16, an exchange alarm display is performed that prompts an exchange of the air filter 5 (step S11). |
