Illumination system, control method for illumination system, and non-transitory computer-readable recording medium

An illumination system, comprising:

• a plurality of light sources configured to emit excitation light, the plurality of light sources including a first light source and a second light source;
• a substrate;
• a plurality of wavelength converters on the substrate, the plurality of wavelength converters including a first wavelength converter configured to emit fluorescence with a first wavelength spectrum in response to excitation light from the first light source and a second wavelength converter configured to emit fluorescence with a second wavelength spectrum different from the first wavelength spectrum in response to excitation light from the second light source;
• a light guide configured to guide fluorescence emitted from the plurality of wavelength converters;
• and
• a controller configured to cause each of the plurality of light sources to repeat emission and non-emission of excitation light in constant cycles,
• wherein when the controller causes each of the plurality of light sources to repeat emission and non-emission of excitation light in the constant cycles, in an operation period of one cycle from a first start timing at which the first light source starts a first irradiation toward the first wavelength converter with excitation light to a second start timing at which the first light source starts a second irradiation subsequent to the first irradiation toward the first wavelength converter with excitation light, the controller causes the second light source to emit no excitation light toward the second wavelength converter for at least a portion of a first emission period during which the first light source emits excitation light toward the first wavelength converter, and the controller causes the first light source to emit no excitation light toward the first wavelength converter for at least a portion of a second emission period during which the second light source emits excitation light toward the second wavelength converter.