a light source which is a flash discharge tube;

an optical element which directs light from the light source to an irradiation direction, said optical element having incident and exit surfaces; and

a reflector which directs the light from said light source to the irradiation direction, said reflector having a half-cylindrical part that covers a back of the light source and is concentric to the light source, and first and second reflective surfaces that respectively extend from first and second circumferential ends of the half-cylindrical part,

wherein first and second areas are defined on a first plane as those divided by a second plane, the first plane being orthogonal to a longitudinal direction of the light source and including an irradiation optical axis, and the second plane being orthogonal to the first plane and including the irradiation optical axis,

wherein an inclination of the exit surface in the first area to a direction orthogonal to the irradiation optical axis is greater than that in the second area, and the inclination in the first area gradually increases in order from the irradiation optical axis, an intermediate part and a periphery,

wherein the light source is decentered to the first area with respect to a centerline that passes a center of an aperture height of the optical element, and the half-cylindrical part is rotated such that the first circumferential end is closer to the optical element than the second circumferential end, the first reflective surface being shorter than the second reflective surface,

wherein the first reflective surface reflects to the exit surface first light that proceeds from said light source to the periphery outside the incident surface in the first area, and the second reflective surface reflects to the exit surface second light that proceeds from said light source to the a periphery outside the incident surface in the second area,

wherein the first reflective surface reflects the first light to the intermediate part in the first area on the exit surface instead of reflecting the first light to the periphery in the first area on the exit surface, and

wherein the second reflective surface reflects the second light to the periphery in the second area on the exit surface instead of reflecting the second light to the intermediate part in the second area on the exit surface.