A light source device, comprising an excitation light source, a wavelength conversion element, a transparent substrate, and a light splitter. The wavelength conversion element comprises a wavelength conversion area and a scattering area. The excitation light source emits excitation light that has a first polarization state. The transparent substrate guides first part of the excitation light to the scattering area and guides second part of the excitation light to the light splitter; and the light splitter guides, directly or by means of a guiding device, the second part of the excitation light to the wavelength conversion area. The scattering area scatters the first part of the excitation light and guides the scattered first part of the excitation light to the transparent substrate; and the transparent substrate and the light splitter guide the scattered first excitation light to a light-emitting channel directly or by means of the guiding device.