To wholly change nonpolarized light emitted from a light source into identical linearly polarized light and to uniformly illuminate the whole objective area by using a thin plate type device having both flat front and back faces as a polarizing separating device.

A first cholesteric liquid crystal device 16 is a thin plate type device having both flat front and back faces. Nonpolarized light from a reflector 12 transmitted through a first lens array 14 is separated into the reflected light which is right-handed circularly polarized light and the transmitted light which is left-handed circularly polarized light. The light transmitted through the first cholesteric liquid crystal device 16 enters a second cholesteric liquid crystal device 17. The cholesteric liquid crystal device 17 is also a thin plate type and it reflects the left-handed circularly polarized light and transmits the right- handed circularly polarized light. Therefore, the optical paths of the light reflected by the cholesteric liquid crystal device 16 and the optical paths of the light reflected by the cholesteric liquid crystal device 17 are alternately distributed at an almost equal interval.