were not shown in fig however the holding component 18 the line 19 the terminal device 23 and the like which are shown in fig5 are not shown in fig2 a and 2 b fig2 a shows mainly the passage for evacuation of the cooling air in the cross section while fig2 b shows mainly the inlet passage for the cooling air in the cross section first blowing of the admitted cooling air out into the light irradiation chamber 1 and the evacuation of the cooling air are described using fig2 a in fig2 a the cooling air admitted into the duct 30 passes through the cooling air exhaust opening 30 c see fig1 located in the bottom of the duct 30 and passes through the cooling air exhaust openings 5 a located in the mirror 5 the cooling air is blown out onto the side of the light irradiation chamber 1 cools the emitting tube portions 7 of the lamps 4 passes through the openings 6 of the mirror 5 and is admitted into the hollow area 30 a the hollow area 30 a of the duct 30 is provided with a gap 30 d as is shown in fig1 a ventilation passage for evacuation is formed by the closing of the bottom side of the hollow area 30 a by the back of the mirror 5 and the top side by the plate 10 the cooling air which has been admitted into the hollow area 30 a with a high temperature is evacuated via this ventilation path for evacuation through the evacuation opening 20 a of the outlet channel 20 the cooling air which cools.