Patent ID: 8334783

Claim:
A projection display device that enlarges and projects an image formed by a display element through a projection lens onto a screen, the display device comprising: a suction fan that draws air from outside of the device through an inlet into the device and blows the cooling air to the display element; a dustproof filter that is arranged in the vicinity of the inlet and removes dust and a foreign material from the drawn air; an air guide path that guides, to the display element, the cooling air blown by the suction fan; an air velocity detector that is arranged in the air guide path and detects the velocity of the cooling air that flows in the air guide path; and a controller that determines, on the basis of the value detected by the air velocity detector, whether or not the dustproof filter is clogged; wherein the air velocity detector includes a reference temperature sensor that measures the temperature of the cooling air that flows in the air guide path, a heat generating element that generates a predetermined amount of heat, and a heater-vicinity temperature sensor that measures the temperature of air in the vicinity of the heat generating element that will be increased due to heat transfer generated by the heat generating element, the reference temperature sensor, the heat generating element and the heater-vicinity temperature sensor of the air velocity detector are arranged, within a flow path for the cooling air at the air guide path, in order of the reference temperature sensor, the heat generating element, and the heater-vicinity temperature sensor from the suction fan side, and the air velocity detector detects the velocity of the cooling air on the basis of a difference between the temperature measured by the reference temperature sensor and the temperature measured by the heater-vicinity temperature sensor.