the temperature on the emission side of the wind is relatively high in addition since the temperature gradients can be averaged the highest temperature in the light valve means in question can be suppressed and as a result the cooling efficiency is increased according to the second embodiment of the present invention there is exhibited an effect of an improved cooling efficiency of the light valve means and components in close proximity to the light valve means 0085 fig1 is a diagram showing branching of ducts in a third embodiment of the present invention as shown in fig1 a wind blown by the centrifugal fan 0 is split at a wind guiding path 714 into a wind going to the light valve means 414 and a wind proceeding through a wind guiding path 715 the wind proceeding through the wind guiding path 715 is further split at a branch portion into a wind going to a space 718 between the first collimator 301 and the second integrator lens 203 and a wind proceeding to a space 780 between the light source 101 and the first integrator lens 401 the wind that further blows forward to the space 718 between the first collimator 301 and the second integrator lens 203 cools the first collimator 301 and the second integrator lens 203.