Abstract: A flat plate collimator and backlight system capable of improving the display characteristics of liquid crystal display devices are obtained. In order to achieve this end, a collimator is provided which comprises a cholesteric liquid crystal layer exhibiting a selective-reflection wavelength band with respect to perpendicularly-incident light in the wavelength range &lgr;1 to &lgr;2 (&lgr;1<&lgr;2), and which satisfies the relation &lgr;0<&lgr;1 with respect to the maximum-emission wavelength &lgr;0 in the emission spectrum of the light source with which the collimator is used in combination, and a backlight system employing this collimator and light source is provided.