Patent ID: 8123362

Claim:
A projector comprising: an optical system unit; a lamp unit having (i) a light emitting unit, (ii) a concave reflecting mirror, and (iii) a translucent plate, said light emitting unit being a light source of the optical system unit and being located in a center of the concave reflecting mirror, said translucent plate being arranged so as to cover an opening of the concave reflecting mirror to form an inside portion of the concave reflecting mirror; a duct arrangement; and a cooling unit that during operation sends air through the duct arrangement to cool the lamp unit, in which the duct arrangement includes (i) a first exhaust duct located in an air exhaust side of the lamp unit and which connects to the light emitting unit by way of an air exhaust slot formed on the concave reflecting mirror and (ii) a second exhaust duct located in the air exhaust side of the lamp unit and which connects to an outside portion of the concave reflecting mirror, in which an enlarged part is provided in an intermediate position of the first exhaust duct in which said intermediate position, is located between a first opening and a second opening of the first exhaust duct such that during operation the enlarged part receives cooling air which passed through the inside portion of the concave reflecting mirror and does not receive cooling air which passed on the outside portion of the concave reflecting mirror, said first opening being an entrance for the first exhaust duct and being positioned adjacent to the air exhaust slot, formed on the concave reflecting mirror and said second opening being an exit for the first exhaust duct, and in which said enlarged part has a square-shaped cross section area which is larger than that of all other portions of the first duct including a first portion adjacent to the first opening and a second portion directly adjacent to the second opening, the square-shaped cross section area being taken in a direction which is parallel to or substantially parallel to a direction in which the air flows in the enlarged part.