| 摘要 |
A housing (17) that accommodates a light source (1), a display device (3), etc. has an intake aperture (18) and an exhaust aperture (24). A blowing unit (16, 23) sucks air in through the intake aperture and expels air out through the exhaust aperture. A filter unit (19) is disposed so that a filter (20) faces the intake aperture in a predetermined area between a rolling shaft (31a) and a take-up shaft (31b). A part of the filter facing the intake aperture is renewed by taking-up the filter from the rolling shaft onto the take-up shaft. A control unit (36) performs control so as to renew the filter for a range that is smaller than an opening area of the intake aperture, when a predetermined renewal condition is determined to be satisfied, based on the output of a detection unit (38, 39a, 39b) that detects a specific factor value relating to contamination of the filter, such as a cumulative display time, a temperature, an air pressure, etc. This reduces a noise occurring during the driving of a fan or a change in the rotational speed of the fan, which are associated with automatic filter renewal.
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