An optical system comprises a first optical path configured to supply a first light with a first range of wavelengths; a second optical path configured to supply a second light with a second range of wavelengths shorter than the first range of wavelengths; a third optical path configured to supply a third light with a third range of wavelengths shorter than the second range of wavelengths; an optical I/O unit configured to emit the first light, the second light and the third light to a target and acquire a light from the target; a reference unit configured to split off a reference light from the third light; and a detector that includes a range of detection wavelengths shared with a CARS light and an interference light.