| 摘要 |
PROBLEM TO BE SOLVED: To prevent a liquid crystal panel from being damaged by heat by forcedly reducing a light quantity from a lamp by controlling the power source of the lamp irradiating the liquid crystal panel when the number of revolution is abnormally changed by comparing a detected result and a set value by providing a means detecting the rotation of the fan of an air blowing device. SOLUTION: An optical device 12 having a liquid crystal panel 11 and a light source 16 irradiating the optical device 12 are arranged at the inside of a housing 10, and also the fan 27 cooling at least the liquid crystal panel 11 is provided. Also, the number of revolution of the fan 27 is detected by a detector for the number of revolution 33, and whether the number of revolution is a normal value or not is discriminated by comparing it with the set value by a discriminating unit for the number of revolution 34. The light quantity from the light source is forcedly reduced by controlling the power source of the light source 16 at the time of abnormally rotating, and the liquid crystal panel 11 is protected by lowering the light quantity of light radiated to the liquid crystal panel 11, so that a damage and the deterioration of a characteristic caused by heat are prevented.
|
