PURPOSE: To reduce the number of parts and the cost of production, by forming a light shielding body in one body to the housing of an exposure optical system which has guide rail surfaces for a movable plate of the optical system on both side faces facing each other, and has a mounting seat for a projection lens at the center of the bottom wall.
CONSTITUTION: The housing of an exposure optical system is provided with a bottom wall 16 of an approximately a square shape and end walls 17 (17A, 17B) and side walls, and many wind passage holes 19 are provided to the walls 17 and the side walls. The housing can be fixed to the frame of a machine body by screwing mounting screws 21 into the mounting holes 20 formed at four corners of the wall 16. Since the holes 19 are communicated with the space C between the housing Y of the machine body and the frame of the machine body in an assembled state, convection or blow-by of the wind in the machine is generated in the housing of the exposure optical system, whereby the overheating of the exposure optical system is prevented.
NOSAKA ISAO
KATAKURA HIROSHI
