A light source device includes a light emitting element and a wavelength conversion device. The wavelength conversion device includes a stationary member, a moveable carrier made of a transparent material carrying one or more wavelength conversion materials and moveable relative to the stationary member, and a stationary first filter. The first filter is fixed on the stationary member and disposed adjacent the moveable carrier. The excitation light from the light emitting element passes through the first filter and illuminates the wavelength conversion materials on the moveable carrier. The wavelength conversion materials convert the excitation light into converted light as the output of the light source device. The size of the first filter is smaller than the size of the moveable carrier and smaller than a carrying area of the moveable carrier that carries the wavelength conversion material. A wavelength conversion method using the wavelength conversion device is also described.