Patent ID: 7997736

Claim:
A projection type video display apparatus for projecting imaging light that is obtained by modulating light emitted from a light source by video signals, the projector equipped with a filter clogging detection system for detecting clogging of a filter for a cooling fan sucking air through the filter to cool heat generating components of the projector, the filter clogging detection system comprising: switching means for switching the operational mode of the cooling fan between a lowland mode and a highland mode; and a controller to obtain a current fan voltage to determine a normal rpm value corresponding to the current fan voltage in reference to a lowland voltage-rpm characteristic when the switching means is in the lowland mode, obtain a current fan rpm, and enable an alarming means to issue a filter clogging alarm in the event that the current fan rpm is larger than the normal rpm value plus a predetermined value, and obtain a current fan voltage to determine a normal rpm value corresponding to the current fan voltage in reference to a highland voltage-rpm characteristic when the switching means is in the highland mode, obtain a current fan rpm, and enable the alarming means to issue a filter clogging alarm in the event that the current fan rpm is larger than the normal rpm value plus a predetermined value.