LIGHT SOURCE DEVICE

A light source device includes a plurality of LEDs, a collimating optical system disposed corresponding to the plurality of LEDs, a condensing optical system that condenses light exiting from the collimating optical system, and a fly-eye integrator into which the light exiting from the condensing optical system is incident. Assuming that parallel light is defined as a virtual secondary light source, the parallel light being obtained from light traveling from a virtual primary light source disposed at a back focus position of the condensing optical system toward the condensing optical system with a maximum effective acceptance angle of the fly-eye integrator as a divergence angle and then passing through the condensing optical system, the virtual secondary light source has a width that substantially coincides with a width of a secondary light source determined according to a shape of a light exit surface of the collimating optical system.