PURPOSE: To prevent a panel sheet being thermally transformed from display disorder due to the heat of illuminating light by cooling a heating coil absorbing filter by one cooling fan and cooling the panel sheet by the other cooling fan.

CONSTITUTION: Since a heat ray included in an optical path can be absorbed by the heat ray absorbing filter 8 and the filter 8 can be cooled by a cooling fan 9, the heat absorbing efficiency is accelerated. The thermo-transformation panel sheet 3 is cooled by a cooling fan 10 and a thermotank 12 absorbs heat discharged from the sheet 3 to uniform the temperature of the whole surface of the sheet 3. Consequently, the light transmissivity or absorbing ratio can be normally changed in accordance with input even at any portion of the sheet 3 and a bright and even projection image as a whole can be projected.