PURPOSE: To decrease the luminous fluxes which is shed out of a light valve and are wasted and to improve luminance by collimating the luminous flux emitted from a light source part to collimated luminous fluxes of a rectangular shape about the size of the light valve.
CONSTITUTION: The light source part 30 is a reflecting mirror 31 of a concave face which is formed as a paraboloid in its section. The focal lengths of the paraboloidal mirrors 40a, 40b, 40c of the concave faces forming sectorial shapes which are a part of the reflecting mirror 39 are varied by the positions ϕ a , ϕ b , ϕ c around the optical axes of rays 35a, 35b, 35c. The luminous fluxes shed out of the light valve among the luminous fluxes with which the light valve is irradiated are decreased and the light valve is eventually irradiated with all the luminous fluxes if the paraboloidal shapes are so constituted that the sectional shape of the collimated luminous fluxes have the same shape and same size as the shape and size of the light valve. The luminance of the projected image projected by a projecting lens is improved in this way.